#include <bits/stdc++.h>
using namespace std;
inline int getint() {
  int res = 0, fh = 1;
  char ch = getchar();
  while ((ch < '0' || ch > '9') && ch != '-') ch = getchar();
  if (ch == '-') fh = -1, ch = getchar();
  while (ch <= '9' && ch >= '0') res = res * 10 + ch - '0', ch = getchar();
  return res * fh;
}
char s[1000001];
int n;
unsigned int f[2][1000001];
int main() {
  n = getint();
  scanf("%s", s + 1);
  f[0][0] = 1;
  for (int i = 1; i <= n; i++) {
    int now = i & 1, pre = now ^ 1;
    int maxx = min(i, n - i), minn = now ? 1 : 2;
    if (s[i] == '?') {
      f[now][0] = f[pre][1];
      for (int j = minn; j <= maxx; j += 2) {
        f[now][j] = f[pre][j - 1] * 25 + f[pre][j + 1];
      }
    } else {
      f[now][0] = 0;
      for (int j = minn; j <= maxx; j += 2) {
        f[now][j] = f[pre][j - 1];
      }
    }
  }
  printf("%u\n", f[n & 1][0]);
  return 0;
}
