#include <bits/stdc++.h>
using namespace std;
template <typename T, typename U>
inline void smin(T &a, const U &b) {
  if (a > b) a = b;
}
template <typename T, typename U>
inline void smax(T &a, const U &b) {
  if (a < b) a = b;
}
template <typename T>
inline void gn(T &first) {
  char c, sg = 0;
  while (c = getchar(), (c > '9' || c < '0') && c != '-')
    ;
  for ((c == '-' ? sg = 1, c = getchar() : 0), first = 0; c >= '0' && c <= '9';
       c = getchar())
    first = (first << 1) + (first << 3) + c - '0';
  if (sg) first = -first;
}
template <class T, class T1>
inline void gn(T &first, T1 &second) {
  gn(first);
  gn(second);
}
template <class T, class T1, class T2>
inline void gn(T &first, T1 &second, T2 &z) {
  gn(first);
  gn(second);
  gn(z);
}
template <typename T>
inline void print(T first) {
  if (first < 0) {
    putchar('-');
    return print(-first);
  }
  if (first < 10) {
    putchar('0' + first);
    return;
  }
  print(first / 10);
  putchar(first % 10 + '0');
}
template <typename T>
inline void println(T first) {
  print(first), putchar('\n');
}
template <typename T>
inline void printsp(T first) {
  print(first), putchar(' ');
}
template <class T, class T1>
inline void print(T first, T1 second) {
  printsp(first), println(second);
}
template <class T, class T1, class T2>
inline void print(T first, T1 second, T2 z) {
  printsp(first), printsp(second), println(z);
}
int power(int a, int b, int m, int ans = 1) {
  for (; b; b >>= 1, a = (long long)a * a % m)
    if (b & 1) ans = (long long)ans * a % m;
  return ans;
}
int num, cnt, u, v;
void calc(int a, int b) {
  if (a < b) swap(a, b);
  u = a, v = b;
  if (v == 0) return;
  if (u == 1 && v == 1) return;
  if (a % b) {
    num += a / b;
    cnt += a / b - 1;
    calc(a % b, b);
  } else if (v != 1)
    return;
  else {
    num += u - 1;
    cnt += u - 2;
    calc(1, 1);
  }
}
vector<int> s;
void solve(int a, int b) {
  if (a < b) swap(a, b);
  if (a == 1 && b == 1) return;
  if (a % b) {
    s.push_back(a / b);
    solve(a % b, b);
  } else {
    s.push_back(a - 1);
    return;
  }
}
int main() {
  int n, r, mn = 0x3f3f3f3f, id;
  gn(n, r);
  n--;
  for (int i = 1; i <= r; i++) {
    num = cnt = 0;
    calc(i, r);
    if (num == n && u == 1 && v == 1 && cnt < mn) {
      mn = cnt;
      id = i;
    }
  }
  if (mn < 0x3f3f3f3f) {
    solve(r, id);
    int f = 0;
    println(mn);
    putchar('T');
    for (int i = s.size(); i--;) {
      char c = f ? 'T' : 'B';
      while (s[i]--) putchar(c);
      f ^= 1;
    }
  } else
    puts("IMPOSSIBLE");
}
