#include <bits/stdc++.h>
using namespace std;
unsigned N, f[100003];
string s;
inline void dp() {
  f[0] = 1;
  for (unsigned i = 1; i <= N; ++i)
    if (s[i] == '?') {
      for (unsigned j = (i >> 1); j; --j) f[j] = 25 * f[j] + f[j - 1];
      f[0] *= 25;
    }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0), cout.tie(0);
  cin >> N;
  if (N & 1) {
    cout << 0;
    return 0;
  }
  cin >> s;
  s = ' ' + s;
  dp();
  cout << f[N >> 1];
  return 0;
}
