#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
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;
    in>>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)
        out<<st;
    else out<<-1;
    return 0;
}