#include <bits/stdc++.h>
template <typename T>
inline T max(T a, T b) {
  return a > b ? a : b;
}
template <typename T>
inline T min(T a, T b) {
  return a < b ? a : b;
}
template <typename T>
inline T abs(T a) {
  return a > 0 ? a : -a;
}
template <typename T>
inline bool repr(T &a, T b) {
  return a < b ? a = b, 1 : 0;
}
template <typename T>
inline bool repl(T &a, T b) {
  return a > b ? a = b, 1 : 0;
}
template <typename T>
inline T gcd(T a, T b) {
  T t;
  if (a < b) {
    while (a) {
      t = a;
      a = b % a;
      b = t;
    }
    return b;
  } else {
    while (b) {
      t = b;
      b = a % b;
      a = t;
    }
    return a;
  }
}
template <typename T>
inline T sqr(T x) {
  return x * x;
}
struct Cg {
  inline char operator()() { return getchar(); }
};
struct Cp {
  inline void operator()(char x) { putchar(x); }
};
inline bool IS(char x) { return x == 10 || x == 13 || x == ' '; }
template <typename T>
struct Fr {
  T P;
  inline Fr &operator,(int &x) {
    x = 0;
    char t = P();
    while ((t < '0' || t > '9') && t != '-') t = P();
    bool f = 0;
    if (t == '-') t = P(), f = 1;
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    if (f) x = -x;
    return *this;
  }
  inline operator int() {
    int x;
    *this, x;
    return x;
  }
  inline Fr &operator,(long long &x) {
    x = 0;
    char t = P();
    while ((t < '0' || t > '9') && t != '-') t = P();
    bool f = 0;
    if (t == '-') t = P(), f = 1;
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    if (f) x = -x;
    return *this;
  }
  inline operator long long() {
    long long x;
    *this, x;
    return x;
  }
  inline Fr &operator,(char &x) {
    for (x = P(); IS(x); x = P())
      ;
    return *this;
  }
  inline operator char() {
    char x;
    *this, x;
    return x;
  }
  inline Fr &operator,(char *x) {
    char t = P();
    for (; IS(t); t = P())
      ;
    if (~t) {
      for (; !IS(t) && ~t; t = P()) *x++ = t;
    }
    *x++ = 0;
    return *this;
  }
  inline Fr &operator,(double &x) {
    x = 0;
    char t = P();
    while ((t < '0' || t > '9') && t != '-') t = P();
    bool f = 0;
    if (t == '-') t = P(), f = 1;
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    if (t == '.') {
      double u = 0.1;
      for (t = P(); t >= '0' && t <= '9'; t = P(), u *= 0.1) x += u * (t - '0');
    }
    if (f) x = -x;
    return *this;
  }
  inline operator double() {
    double x;
    *this, x;
    return x;
  }
  inline Fr &operator,(long double &x) {
    x = 0;
    char t = P();
    while ((t < '0' || t > '9') && t != '-') t = P();
    bool f = 0;
    if (t == '-') t = P(), f = 1;
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    if (t == '.') {
      double u = 0.1;
      for (t = P(); t >= '0' && t <= '9'; t = P(), u *= 0.1) x += u * (t - '0');
    }
    if (f) x = -x;
    return *this;
  }
  inline operator long double() {
    long double x;
    *this, x;
    return x;
  }
  inline Fr &operator,(unsigned int &x) {
    x = 0;
    char t = P();
    while (t < '0' || t > '9') t = P();
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    return *this;
  }
  inline operator unsigned int() {
    unsigned int x;
    *this, x;
    return x;
  }
  inline Fr &operator,(unsigned long long &x) {
    x = 0;
    char t = P();
    while (t < '0' || t > '9') t = P();
    x = t - '0';
    for (t = P(); t >= '0' && t <= '9'; t = P()) x = x * 10 + t - '0';
    return *this;
  }
  inline operator unsigned long long() {
    unsigned long long x;
    *this, x;
    return x;
  }
};
Fr<Cg> in;
template <typename T>
struct Fw {
  T P;
  inline Fw &operator,(int x) {
    if (x) {
      if (x < 0) P('-'), x = -x;
      char s[10], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator()(int x) {
    if (x) {
      if (x < 0) P('-'), x = -x;
      char s[10], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator,(unsigned int x) {
    if (x) {
      char s[10], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator()(unsigned int x) {
    if (x) {
      char s[10], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator,(long long x) {
    if (x) {
      if (x < 0) P('-'), x = -x;
      char s[19], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator()(long long x) {
    if (x) {
      if (x < 0) P('-'), x = -x;
      char s[19], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator,(unsigned long long x) {
    if (x) {
      char s[20], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator()(unsigned long long x) {
    if (x) {
      char s[20], c = 0;
      while (x) s[c++] = x % 10 + '0', x /= 10;
      while (c--) P(s[c]);
    } else
      P('0');
    return *this;
  }
  inline Fw &operator,(char x) {
    P(x);
    return *this;
  }
  inline Fw &operator()(char x) {
    P(x);
    return *this;
  }
  inline Fw &operator,(const char *x) {
    while (*x) P(*x++);
    return *this;
  }
  inline Fw &operator()(const char *x) {
    while (*x) P(*x++);
    return *this;
  }
  inline Fw &operator()(double x, int y) {
    if (y) {
      double t = 0.5;
      for (int i = y; i--;) t *= 0.1;
      if (x >= 0)
        x += t;
      else
        x -= t, P('-');
      *this, (long long)(abs(x));
      P('.');
      if (x < 0) x = -x;
      while (y--) {
        x *= 10;
        x -= floor(x * 0.1) * 10;
        P(((int)x) % 10 + '0');
      }
    } else if (x >= 0)
      *this, (long long)(x + 0.5);
    else
      *this, (long long)(x - 0.5);
    ;
    return *this;
  }
  inline Fw &operator()(long double x, int y) {
    if (y) {
      double t = 0.5;
      for (int i = y; i--;) t *= 0.1;
      if (x >= 0)
        x += t;
      else
        x -= t, P('-');
      *this, (long long)(abs(x));
      P('.');
      if (x < 0) x = -x;
      while (y--) {
        x *= 10;
        x -= floor(x * 0.1) * 10;
        P(((int)x) % 10 + '0');
      }
    } else if (x >= 0)
      *this, (long long)(x + 0.5);
    else
      *this, (long long)(x - 0.5);
    ;
    return *this;
  }
};
Fw<Cp> out;
const int N = 300007, P = 1000000007;
int n, al, bl, po[N], fac[N * 2], fin[N * 2];
long long cnt[N];
char a[N], b[N];
inline int pow(int a, int b) {
  int r = 1;
  for (; b; b >>= 1, a = (long long)a * a % P)
    if (b & 1) r = (long long)r * a % P;
  return r;
}
inline int C(int n, int m) {
  return (long long)fac[n] * fin[m] % P * fin[n - m] % P;
}
int main() {
  in, a, b, n;
  al = strlen(a), bl = strlen(b);
  po[0] = 0;
  for (int i = 1, iend = n; i <= iend; i++) po[i] = (po[i - 1] * 2 + 2) % P;
  int ac = 0, bc = 0, qc = 0;
  for (int i = 0, iend = al; i < iend; i++)
    if (a[i] == 'A')
      ac++;
    else if (a[i] == 'B')
      bc--;
    else
      qc++, bc--;
  for (int i = 0, iend = bl; i < iend; i++)
    if (b[i] == 'A')
      ac--;
    else if (b[i] == 'B')
      bc++;
    else
      qc++, ac--;
  fac[0] = 1;
  for (int i = 1, iend = qc; i <= iend; i++)
    fac[i] = (long long)fac[i - 1] * i % P;
  fin[qc] = pow(fac[qc], P - 2);
  for (int i = qc; i; i--) fin[i - 1] = (long long)fin[i] * i % P;
  int ans = 0;
  for (int i = 0, iend = qc; i <= iend; i++) {
    int x = ac + i, y = bc + i;
    if (!x && !y) {
      int t = 0, v = C(qc, i);
      for (int j = 0, jend = al; j < jend; j++)
        if (a[j] == '?' && b[j] == '?') t++;
      t = pow(2, t);
      for (int j = 0, jend = al; j < jend; j++)
        if (a[j] != '?' && b[j] != '?' && a[j] != b[j]) t = 0;
      ans = ((long long)po[n] * po[n] % P * t + ans) % P;
      v = (v + P - t) % P;
      t = 0;
      for (int j = n; j; j--) {
        cnt[j] = (long long)(n / j) * (n / j);
        for (int k = j * 2; k <= n; k += j) cnt[j] -= cnt[k];
        t = (t + cnt[j] % P * pow(2, j)) % P;
      }
      ans = ((long long)t * v + ans) % P;
    }
    if ((long long)x * y > 0) {
      x = abs(x), y = abs(y);
      int z = gcd(x, y);
      if (z) x /= z, y /= z;
      ans = ((long long)po[n / max(x, y)] * C(qc, i) + ans) % P;
    }
  }
  out, ans, '\n';
}
