#include <iostream>
#include <fstream>

using namespace std;

int verifica(long long nr){
    long long numitor=5;
    long long suma=0;
    while(nr/numitor>0){
        suma=suma+nr/numitor;
        numitor=numitor*5;
    }
    return suma;
}

long long pas=1<<30;
int main()
{
    long long n,nract;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>n;
    nract=5;
    long long nr=1;
    long long studiaza;

    pas+=1000000000000;
    cout<<(pas);
    long long i;
    for(i=0;pas>0;pas=pas/2){
        if(verifica(i+pas)<n)
            i+=pas;
    }
    g<<i+1;
    return 0;
}