#include <iostream>
#include <fstream>

using namespace std;

ifstream f ("fact.in");
ofstream t ("fact.out");

int nr0(int n)
{
    int i,nr=0;
    for (i=5;i<=n;i*=5)
        nr+=n/i;
    return nr;
}

int main()
{int st,dr,mj,p,k;
    f>>k;
    if (k==0) t<<"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;
        }
        t<<p<<"\n";}
return 0;
}