#include <fstream>
#include<cmath>
using namespace std;
int main()
{
    ifstream f ("fact.in");
    ofstream g ("fact.out");
    int n,ls,ld,b,p,x,a;
    ls=5;
    ld=400000015;
    b=0;
    f>>p;
    if(p==0)
    {
        x=1;
        g<<"1";
    }
    else
    {
        n=0;
            while(ls<=ld && b==0)
            {
                n=(ls+ld)/2;
                x=0;
                a=5;
                while(a<=n)
            {
                    x=x+n/a;
                    a=a*5;
            }
        if(x==p)
        {
            g<<(n/5)*5;
            b=1;
        }
        else
            if(x<p)
                ls=n+1;
        else
            ld=n-1;
            }
            if(b==0)
                g<<"-1";
    }
}