#include <bits/stdc++.h>
using namespace std;
template <typename T>
void read(T &a) {
  register int b = 1, c;
  a = 0;
  for (c = fgetc(stdin); c > 57 || c < 48; c = fgetc(stdin))
    if (c == 45) b = -1;
  for (; c >= 48 && c <= 57; c = fgetc(stdin)) a = a * 10 + c - 48;
  a *= b;
}
int n;
char s[100005];
unsigned int dp[100005];
int main() {
  read(n);
  scanf("%s", s + 1);
  int q = 0;
  for (int i = 1; i <= n; i++) {
    if (s[i] == '?') q++;
  }
  if ((n & 1) || q < (n >> 1)) {
    printf("0\n");
    return 0;
  }
  dp[0] = 1;
  for (int i = 1; i <= n; i++) {
    if (s[i] == '?') {
      int lb = max(1, i - (n >> 1)), rb = i >> 1;
      for (int j = rb; j >= lb; j--) dp[j] += dp[j - 1];
    }
  }
  for (int i = 0; i < q - (n >> 1); i++) {
    dp[n >> 1] *= 25;
  }
  printf("%u\n", dp[n >> 1]);
  return 0;
}
