#include <iostream>
#include <fstream>
using namespace std;
long long int n,p,i,nr,ok,k,y,x;
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    while(k<p)
    {
        i++;
        if(i%5==0)
        {
            y=i;
            if(y%5==0){while(y/5!=0){y=y/5;k++;}}
        }


    }
    if(k>p)cout<<"-1";
    else cout<<i;

 return 0;
}