#include <bits/stdc++.h>
using namespace std;
unsigned int dp[100010];
int n, m, maxx;
char str[100010];
int main() {
  cin >> n;
  if (n & 1) {
    cout << 0 << endl;
    return 0;
  }
  scanf("%s", str + 1);
  dp[0] = 1;
  for (int i = 1; i <= n; i++)
    if (str[i] == '?') {
      m++;
      maxx = min(i / 2, m);
      for (int j = maxx; j; j--) dp[j] += dp[j - 1];
    }
  if (m < n / 2) {
    cout << 0 << endl;
    return 0;
  }
  m -= n / 2;
  while (m--) dp[n >> 1] *= 25;
  cout << dp[n >> 1] << endl;
  return 0;
}
