MY SIM SB3 3

#include <iostream>
#include <fstream>
using namespace std;
ofstream fout("bac.txt");

int getCntOfBaseInNFact(int n, int base) {
    int cnt = 0, powOfBase = base;
    while (n / powOfBase) {
        cnt += n / powOfBase;
        powOfBase *= base;
    }
    return cnt;
}

int main() {
    int n;
    cin >> n;
    int fr5 = getCntOfBaseInNFact(n, 5);
    int fr9 = getCntOfBaseInNFact(n, 3) / 2;
    fout << (fr9 > fr5 ? fr5 : fr9) << '\n';
    fout.close();
    return 0;
}