#include <iostream>
using namespace std;
int main() {
int n, prod = 1, zero = 0;
cout << "Introduceti n:";
cin >> n;
for (int i = 1; i <= n; i++) {
prod = prod * i;
}
while (prod % 10 == 0) {
zero++;
prod = prod / 10;
}
cout << endl << zero;
}