#include <bits/stdc++.h>
using namespace std;
const unsigned int N = 2e5 + 10;
inline unsigned int read() {
  register unsigned int x = 0, w = 0;
  register char ch = 0;
  while (!isdigit(ch)) {
    w |= ch == '-';
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 3) + (x << 1) + ch - '0';
    ch = getchar();
  }
  return w ? -x : x;
}
unsigned int f[N];
char ch[N];
int n, p, cnt, Ans;
int main(int argc, char const *argv[]) {
  ios::sync_with_stdio(false);
  cin >> n;
  if (n & 1) return puts("0"), 0;
  cin >> ch + 1;
  p = n >> 1, Ans = 1, f[0] = 1;
  for (register int i = 1; i <= n; ++i) {
    if (ch[i] == '?')
      for (register int j = i >> 1; i - p <= j && j; --j) f[j] += f[j - 1];
    else
      ++cnt;
  }
  for (int i = 1; i <= p - cnt; ++i) Ans = Ans * 25;
  cout << Ans * f[p] << endl;
  return 0;
}
