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

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

long long p,x,st,dr,mij,m5,s,ok;

int main()
{
    in>>p;
    if(p==0)
        out<<"1";
    else
    {
        st=5;
        dr=400000015;
        while(st<=dr)
        {
            mij=(st+dr)/2;
            x=mij;
            m5=5;
            s=0;
            while(x/m5>0)
            {
                s=s+x/m5;
                m5=m5*5;
            }
            if(s==p)
            {
                ok=1;
                break;
            }
            else if(s<p)
                st=mij+1;
            else
                dr=mij-1;
        }
        if(ok==1)
            out<<mij/5*5;
        else
            out<<"-1";
    }
    return 0;
}