#include <bits/stdc++.h>
using namespace std;
const int N = 100005;
int n;
char ch[N];
unsigned f[N];
int main() {
  scanf("%d%s", &n, ch + 1);
  if (n & 1) return puts("0"), 0;
  f[0] = 1;
  int m = n / 2, q = 0;
  for (int i = 1; i <= n; i++)
    if (ch[i] == '?')
      for (int j = i >> 1; n - i + j >= m && j; j--) f[j] += f[j - 1];
    else
      q++;
  for (int i = 1; i <= m - q; i++) f[m] *= 25;
  printf("%u\n", f[m]);
  return 0;
}
