#include <bits/stdc++.h>
using namespace std;
char S[100010];
int N, L, R;
unsigned int dp[100010 * 3];
int main() {
  scanf("%d%s", &N, S);
  dp[L = N + 2] = 1;
  R = L + 1;
  for (int i = 0; i < N; i++) {
    if (S[i] != '?')
      --L;
    else {
      dp[++R] = 0;
      dp[++R] = 0;
      for (int j = R - 1; j >= L + 1; j--) dp[j] += dp[j - 2] * 25;
      dp[L++] = 0;
    }
    if (R - L >= (N - i)) dp[R--] = 0;
  }
  printf("%u\n", dp[L]);
}
