#include<fstream>

std::ifstream f("fact.in");
std::ofstream g("fact.out");

int contor5(int n)
{
    int c=0, i;

    for(i=5;i<=n;i*=5)
        c+=n/i;

    return c;

}

int main()
{

    int p,st=1,dr=100000000,m,c5;

    f>>p;

    if(p==0)
        g<<1;
    else
    {
        while(st<=dr)
        {
            m=(st+dr)/2;
            c5=contor5(m);

            if(c5<p)
                st=m+1;
            else
                dr=m-1;
        }

        if(c5==p)
            g<<m-m%5;
        else
            g<<-1;
    }

    return 0;
}