#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, mmax = -1, sol(0);
  cin >> n;
  vector<int> cont(n);
  vector<int> vis(1000100);
  for (int i = 0; i < n; i++) {
    cin >> cont[i];
    vis[cont[i]] = true;
    mmax = max(mmax, cont[i]);
    sol += (cont[i] > 25);
  }
  cout << max(0, mmax - 25) << '\n';
  return 0;
}
