#include <iostream>
#include<fstream>
using namespace std;
long long p,x,i,nr,k;
int main()
{
    ifstream f("fact.in");
    f>>p;
    f.close();
    if(p)
    {
        x=5;nr=1;
        while(nr<p)
        {
            x+=5;k=1;
            i=x/5;while(i%5==0){++k;i/=5;}
            nr+=k;
        }
    }
    else
        x=1;
    ofstream g("fact.out");
    if(nr==p)g<<x;
    else g<<"-1";
    g.close();
    return 0;
}