#include <iostream>
#include <fstream>
#define N 101
using namespace std;

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

int Nr0(int x)
{
    int i,ct=0;

    i=5;
    while(x/i!=0)
    {

        ct+=x/i;
        i*=5;
    }

    return ct;


}


int main()
{
    int st=1,dr=500000000;
    int m,p;
   fin>>p;
    while(st<=dr)
    {
        m=st+(dr-st)/2;
        if(Nr0(m)<p) st=m+1;
        else if(Nr0(m)>p) dr=m-1;
        else {fout<<m-m%5;return 0;}
    }

    fout<<-1;


    return 0;
}