#include <bits/stdc++.h>
using namespace std;
string s;
int q;
int n;
unsigned int dp[100007];
int main() {
  cin >> n;
  cin >> s;
  for (int i = 0; i < ((int)(s).size()); i++)
    if (s[i] == '?') q++;
  if (q < n / 2 || n % 2) return puts("0"), 0;
  dp[0] = 1;
  for (int i = 0; i < n; i++) {
    int minn = max(0, i - n / 2), maxn = i / 2;
    dp[maxn + 1] = 0;
    if (s[i] == '?')
      for (int j = maxn; j >= minn; j--) dp[j + 1] += dp[j];
  }
  unsigned int xx = dp[n / 2];
  for (int i = 0; i < q - n / 2; i++) xx *= 25;
  cout << xx << endl;
  return 0;
}
