#include <bits/stdc++.h>
using namespace std;
int main() {
  int64_t N;
  scanf("%lld", &N);
  vector<int64_t> have(N);
  for (int64_t i = 0; i < N; i++) {
    scanf("%lld", &have[i]);
  }
  sort(have.begin(), have.end());
  int64_t missing = 0;
  for (int64_t i = 1; i <= have.back(); i++) {
    if (find(have.begin(), have.end(), i) == have.end()) missing++;
  }
  printf("%lld\n", ::max<int64_t>(0, missing - (25 - N)));
}
