#include <bits/stdc++.h>
using namespace std;
int n, m;
unsigned int dp[110000];
char str[110000];
int main() {
  scanf("%d", &n);
  scanf("%s", str + 1);
  for (int i = 1; i <= n; i++)
    if (str[i] != '?') m++;
  if (n & 1 || m > n / 2) {
    printf("0\n");
    return 0;
  }
  dp[0] = 1;
  for (int i = 1; i <= n; i++) {
    int l = max(0, i - n / 2), r = i / 2;
    if (str[i] == '?')
      for (int j = r; j >= l; j--) dp[j] += dp[j - 1];
    dp[r + 1] = 0;
  }
  for (int i = 1; i <= n / 2 - m; i++) dp[n / 2] *= 25;
  cout << dp[n / 2] << endl;
  return 0;
}
