#include <iostream>

using namespace std;

int nz(int x)
{
    int ans=0, p5=5;
    while (x>=p5)
    {
        ans=ans+x/p5;
        p5=p5*5;
    }
    return ans;
}

int main()
{
    int p;
    cin>>p;
    int st=1,dr=5*p;
    while (st<=dr)
    {
        int mij=(st+dr)/2;
        if(nz(mij)<p)
            st=mij+1;
        else dr=mij-1;
    }
    if(nz(st)==p)
        cout<<st;
    else cout<<-1;
    return 0;
}