#include <bits/stdc++.h>
using namespace std;
unsigned int dp[100100];
char s[100100];
int main() {
  unsigned int n;
  cin >> n;
  if (n & 1) {
    return !printf("0");
  }
  scanf("%s", s + 1);
  int m = n / 2;
  dp[0] = 1;
  for (int i = 1; i <= n; i++) {
    if (s[i] == '?') {
      for (int j = i / 2; j >= max(1, i - m); j--) dp[j] += dp[j - 1];
    }
  }
  for (int i = 1; i <= n; i++) {
    if (s[i] == '?') continue;
    m--;
  }
  for (int i = 1; i <= m; i++) dp[n / 2] *= 25;
  cout << dp[n / 2] << "\n";
  return 0;
}
