#include <bits/stdc++.h>
using namespace std;
const unsigned int maxn = 2e6 + 10;
unsigned int dp[maxn], n;
char s[maxn];
signed main() {
  cin >> n;
  if (n & 1) {
    printf("0");
    return 0;
  }
  scanf("%s", s + 1);
  dp[0] = 1;
  for (unsigned int i = 1; i <= n; i++)
    if (s[i] == '?') {
      for (unsigned int j = i / 2; j >= 1; j--) dp[j] = dp[j] * 25 + dp[j - 1];
      dp[0] = dp[0] * 25;
    }
  cout << dp[n / 2];
  return 0;
}
