#include <iostream>
#include <fstream>

using namespace std;

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

int zerouri(int x)
{
    int p=5,k=0;
    while(p<=x)
    {
        k+=x/p;
        p=p*5;
    }
    return k;
}

int cautbin(int p)
{
    int st=1,dr=500000000,poz=-1,m;
    while(st<=dr)
    {
        m=st+(dr-st)/2;
        if(zerouri(m)<=p)
        {
            poz=m;
            st=m+1;
        }
        else
            dr=m-1;
    }
    if(zerouri(poz)==p)
        return poz-4;
    else
        return -1;
}

int main()
{
    int p;
    fin>>p;
    if(p==0)
        fout<<1;
    else
        fout<<cautbin(p);
    return 0;
}