#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

long long getzeros(long long n) {
    long long val = 0;
    while (n > 0) {
        val += n/5;
        n /= 5;
    }
    return val;
}

int main() {
    long long p;
    fin >> p;
    long long st = 1, dr = 1e18, answer;
    while (st < dr) {
        long long mij = (st + dr)/2;
        long long cnt = getzeros(mij);
        if (cnt >= p) {
            answer = mij;
            dr = mij;
        }
        else
            st = mij + 1;
    }
    fout << answer << endl;

    return 0;
}