#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
    int n, p, maxx, i=1, nfact=1, cont=0, c=0;
    f>>p;
    if (p==0)
        { g<<"0"; return 0;}
    while (p>0)
    {   c=c+5;
        nfact=nfact*(c-4)*(c-3)*(c-2)*(c-1)*c;
        if (i%5==0) { cont=cont+2; p=p-cont; }
         else --p;
        ++i;
    }
    if (p<0) g<<"-1";
     else g<<c;

    return 0;
}