#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 603;
int n, m, tot;
unsigned int f[maxn];
char s[maxn];
int main() {
  scanf("%d", &n);
  m = n >> 1;
  scanf("%s", s + 1);
  f[0] = 1;
  for (int i = 1; i <= n; i++)
    if (s[i] == '?')
      for (int j = i / 2; j && j >= i - m; j--) f[j] += f[j - 1];
    else
      tot++;
  if ((n & 1) || tot > m) {
    puts("0");
    return 0;
  }
  unsigned int ans = f[m];
  for (int i = 0; i < m - tot; i++) ans *= 25;
  cout << ans << endl;
  return 0;
}
