#include <bits/stdc++.h>
const int maxn = 100005;
int n;
char c;
unsigned int f[maxn];
int main() {
  scanf("%d", &n);
  if (n % 2) {
    puts("0");
    return 0;
  }
  f[0] = 1;
  for (register int i = 1; i <= n; i++) {
    for (c = getchar(); (c < 'a' || c > 'z') && c != '?'; c = getchar())
      ;
    if (c == '?') {
      for (register int j = i / 2; j >= 1; j--) f[j] = f[j] * 25 + f[j - 1];
      f[0] = f[0] * 25;
    }
  }
  printf("%u\n", f[n / 2]);
  return 0;
}
