#include <bits/stdc++.h>
using namespace std;
int n;
char s[100001];
unsigned int dp[100001];
void run(int casenr) {
  scanf("%d %s", &n, s);
  int nquestion = 0;
  for (int i = (0); i < (n); ++i)
    if (s[i] == '?') ++nquestion;
  if (n % 2 == 1 || 2 * nquestion < n) {
    printf("0\n");
    return;
  }
  memset(dp, 0, sizeof(dp));
  dp[0] = 1;
  for (int i = (0); i < (n); ++i) {
    int minclose = max(0, i + 1 - n / 2), maxclose = (i + 1) / 2;
    if (s[i] == '?') {
      for (int j = maxclose; j >= minclose && j >= 1; --j) dp[j] += dp[j - 1];
    }
  }
  unsigned int ret = dp[n / 2];
  for (int i = (0); i < (nquestion - n / 2); ++i) ret *= 25;
  cout << ret << endl;
}
int main() {
  run(1);
  return 0;
}
