#include <fstream>

using namespace std;

int nr(int n)
{
    int p5=5,s=0;
    while(n>=p5)
    {
        s+=n/p5;
        p5*=5;
    }
    return s;
}

int main()
{
    ifstream f("fact.in");
    ofstream fout("fact.out");
    int li=1,lf=2147483647,n0,m,p;
    f>>p;
    while(li<=lf)
    {
        m=(li+lf)/2;
        n0=nr(m);
        if(n0>=p)
            lf=m-1;
        else li=m+1;
    }
        if(nr(li)==p) fout<<li;
        else fout<<-1;
    return 0;
}