#include <fstream>

using namespace std;

fstream in ("fact.in" , ios::in ),
        out("fact.out", ios::out);

int p;

int zero(int x);

int main(){

    in >> p;

    long long pas = 1LL<<50LL, i=0;

    while( pas ){

        if( zero( pas+i ) < p ){

            i+=pas;
        }

        pas/=2;
    }

    out << i+1 <<'\n';

    return 0;
}


int zero(int x){

    int rez = 0;

    while( x>=5 ){

        rez += x/5;
        x /= 5;
    }

    return rez;
}