usaco-practice/cses/Trailing Zeros.cpp

#include <cmath>
#include <iostream>
using namespace std;

int main() {
  long n;
  cin >> n;

  int a = 0;
  for (int i = 0; i < 100; i++) {
    a += floor(n / pow(5, i + 1));
  }
  cout << a;
}