#include <bits/stdc++.h>
using namespace std;
bool vis[1001000];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < (n); ++i) {
    int x;
    scanf("%d", &x);
    vis[x] = 1;
  }
  int ans = 0;
  int rmd = 25 - n;
  for (int i = 1; i <= (1000000); ++i) {
    if (!vis[i]) {
      if (rmd == 0)
        ++ans;
      else
        --rmd;
    } else
      --n;
    if (n == 0) break;
  }
  printf("%d\n", ans);
  return 0;
}
