#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int nr_zerouri(int numar){
    int counter=0;
    for(int i=5;i<=numar;i*=5){
        counter+=numar/i;
    }
    return counter;
}

int main()
{
    int p,ok = 0,l=1,r=1000000000,m;
    f>>p;

    while(l<=r)
    {
        m=l+(r-l)/2;
        if(nr_zerouri(m)==p){
        g<<m;
        ok = 1;
        break;
        }
        if(nr_zerouri(m)<p)
        {
            l=m+1;
        } else {
            r = m-1;
        }
    }
    if (ok==0){
        g<<-1;
    }
    return 0;
}