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