#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int test(int a)
{
    int x=5;
    int nr=0;
    while(x<=a)
    {
        nr+=a/x;
        x*=5;
    }
    return nr;
}
int p,n,st,dr,x,mid;
int main()
{
    f>>p;
    st=1;
    dr=2000000000;
    if(p==0) {g<<1;return 0;}
    while(st<=dr)
    {
        mid=(st+dr)/2;
        x=test(mid);
        if(x<p)
        {
            st=mid+1;
        }
        else
            dr=mid-1;
    }
    if(test(st)==p)
    {
        g<<st;
    }

    else
        g<<-1;
    return 0;
}