#include <bits/stdc++.h>
using namespace std;
const int maxn = 100000 + 15;
char st[maxn];
int n;
unsigned int f[maxn];
int main() {
  scanf("%d", &n);
  if (n & 1) {
    printf("0\n");
    return 0;
  }
  scanf("%s", st);
  int q = 0;
  for (int i = 1; i <= n; i++)
    if (st[i - 1] != '?') q++;
  if (q > n / 2) {
    printf("0\n");
    return 0;
  }
  f[0] = 1;
  for (int i = 1; i <= n; i++)
    if (st[i - 1] == '?')
      for (int j = i / 2, minn = max(1, i - n / 2); j >= minn; j--)
        f[j] += f[j - 1];
  unsigned ans = f[n / 2];
  for (int i = n / 2 - q; i > 0; i--) ans *= 25;
  cout << ans << endl;
  return 0;
}
