#include <bits/stdc++.h>
using namespace std;
int n, p;
char c[100005];
unsigned int f[50005] = {1}, ans = 1;
int main() {
  scanf("%d", &n);
  if (n % 2 == 1) {
    printf("0\n");
    return 0;
  }
  scanf("%s", c + 1);
  for (int i = 1; i <= n; i++) {
    if (c[i] == '?') {
      for (int j = i / 2; j >= i - n / 2 && j; j--) {
        f[j] += f[j - 1];
      }
    } else
      p++;
  }
  for (int i = 1; i <= n / 2 - p; i++) ans *= 25;
  cout << ans * f[n / 2];
  return 0;
}
