#include<fstream>
using namespace std;
long st,dr,mij,p;
long zerouri(long n)
    {
        long z=0;
        while(n>0)
            {
                z=z+n/5;
                n=n/5;
            }
        return z;
    }
int main()
{
    ifstream f("fact.in");
    ofstream g("fact.out");
f>>p;
st=1;dr=1000000000;
while(st<=dr)
    {
        mij=(st+dr)/2;
        if(zerouri(mij)<p)
            st=mij+1;
        else dr=mij-1;
    }
if(zerouri(st)==p)
    g<<st;
else if(p==0)
    g<<1;
else
    g<<-1;
return 0;
}