#include <bits/stdc++.h>
using namespace std;
unsigned int dp[100005];
int n;
char str[100005];
int main() {
  scanf("%d", &n);
  if (n & 1) {
    puts("0");
    return 0;
  }
  scanf("%s", str + 1);
  int q = 0;
  for (int i = 1; i <= n; i++) {
    if (str[i] != '?') q++;
  }
  if (q > (n >> 1)) {
    puts("0");
    return 0;
  }
  dp[0] = 1;
  for (int i = 1; i <= n; i++) {
    int l = max(1, i - (n >> 1)), r = i >> 1;
    if (str[i] == '?')
      for (int j = r; j >= l; j--) dp[j] += dp[j - 1];
  }
  unsigned int ans = dp[n >> 1];
  q = (n >> 1) - q;
  for (int i = 0; i < q; i++) ans = ans * 25;
  printf("%u\n", ans);
  return 0;
}
