#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int main(){
	long long n,i,j,s=1,p=-5,h=1,x=0;
	in>>n;
	if(n==25)
    {
        out<<"-1";
        return 0;
    }
	long long aux;
	aux=n;
    aux=aux*5;
	if(n==0)
    {
        out<<"-1";
        return 0;
    }
	for(i=1;i<=100000000;i++)
    {
        s=s*5;
        p=p+5;
        h=h+x;
        x++;
        n=h+x-1;
        if(s>aux)
        {
            out<<aux;
            return 0;
        }
        if(s==n)
        {
            out<<"-1";
            return 0;
        }
        if(s<aux)
        {
            aux=aux-p;
        }


    }
}