#include <bits/stdc++.h>
using namespace std;
using U = unsigned int;
const int N = 1e5 + 10;
char s[N];
U dp[N];
U power(U a, int b, U ans = 1) {
  for (; b; b >>= 1, a *= a) {
    if (b & 1) ans *= a;
  }
  return ans;
}
int main() {
  int n, m = 0;
  scanf("%d %s", &n, s);
  for (int i = 0; i < n; i++) m += s[i] != '?';
  if (n & 1 || m > n / 2) {
    puts("0");
    return 0;
  }
  dp[0] = 1;
  for (int i = 0; i < n; i++) {
    if (s[i] == '?') {
      for (int j = i + 1 >> 1; j--;) {
        dp[j + 1] += dp[j];
      }
    }
  }
  cout << dp[n / 2] * power(25, n / 2 - m) << endl;
  return 0;
}
