#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int k;
int Nr0(int n)
{
    int i,nr=0;
    for (i=5;i<=n;i*=5)
        nr+=(n/i);
    return nr;
}
int main()
{
    int i,st,dr,mj,p;
    fin>>k;
    if (k==0) fout<<"1"<<"\n";
    else
    {
        st=1; dr=500000000;
        p=-1;
        while(st<=dr)
        {
            int x;
            mj=st+(dr-st)/2;
            x=Nr0(mj);
            if (x==k)
            {
                p=mj;
                dr=mj-1;
            }
            else if (x<k) st=mj+1;
                 else dr=mj-1;
        }
        fout<<p<<"\n";
    }
    fin.close();
    fout.close();
    return 0;
}