#include <bits/stdc++.h>
using namespace std;
int n;
string s;
unsigned int dp[100010];
int main() {
  ios::sync_with_stdio(false);
  cin >> n >> s;
  if (n & 1) {
    cout << 0 << endl;
    return 0;
  }
  s = ' ' + s;
  dp[0] = 1;
  int times = n / 2;
  for (int i = 1; i <= n; i++) {
    if (s[i] != '?')
      times--;
    else
      for (int j = i / 2; j > 0 && j >= i - n / 2; j--) dp[j] += dp[j - 1];
  }
  unsigned int ans = dp[n / 2];
  while (times > 0) ans *= 25, times--;
  cout << ans << endl;
  return 0;
}
