#include <bits/stdc++.h>
using namespace std;
char str[100005];
unsigned int dp[50005];
int main() {
  int n;
  scanf("%d\n", &n);
  gets(str);
  dp[0] = 1;
  int cnt = 0;
  for (int i = 1; i <= n; ++i) {
    if (str[i - 1] == '?') {
      unsigned int add = dp[0];
      dp[0] = 0;
      int up = min(i, n / 2);
      for (int j = 1; j <= up; ++j) {
        dp[j - 1] += dp[j];
        swap(add, dp[j]);
      }
    } else {
      ++cnt;
      for (int j = min(i, n / 2); j >= 0; --j) dp[j + 1] = dp[j];
      dp[0] = 0;
    }
  }
  for (int i = (n / 2 - cnt); i > 0; --i) dp[0] *= 25;
  cout << dp[0] << endl;
  return 0;
}
