#include <iostream>
#include <fstream>
using namespace std;

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

int main()
{
    int p,i,n,k=1;
    fin>>p;
    if(p>100)
    {
        i=p;
        while(i>9)
        {
            k*=10;
            i/=10;
        }
        p-=k;
        k=k*4+10;
    }
    else
        k=5;
    for(n=k;p>0;n+=5)
    {
        i=n;
        while(i%5==0)
        {
            p--;
            i/=5;
        }
    }
    if(n<=5)
        fout<<1;
    else
        if(p==0)
            fout<<n-5;
            else
                fout<<-1;
}