#include <bits/stdc++.h>
using namespace std;
int a;
char c[100009];
unsigned int dp[200009] = {1};
int main() {
  scanf("%d%s", &a, c);
  for (int i = a; i >= 1; i--) {
    c[i] = c[i - 1];
  }
  if (a & 1) {
    cout << 0;
  } else {
    int e = a >> 1;
    int q = 0;
    for (int i = 1; i <= a; i++) {
      if (c[i] == '?') {
        for (int j = (i >> 1); j >= i - e && j > 0; j--) {
          dp[j] += dp[j - 1];
        }
      } else {
        q++;
      }
    }
    unsigned int ans = dp[e];
    for (int i = 1; i <= e - q; i++) {
      ans *= 25;
    }
    cout << ans;
  }
  return 0;
}
