#include <fstream>
#include <iostream>
using namespace std;
ifstream fin ("fact.in");
ofstream fout("fact.out");
int a,p,i,m,n,x,r,j;
long long st,dr,mid;
int main () {
    fin>>p;
    if(p==0){
        fout<<1;
        return 0;
    }
    st=1;
    dr=5;
    while(x<p){
        x=x+st;
        st=st*5;
        dr=dr*5;
    }
    st/=5;
    dr/=5;
    while(st<=dr){
        mid=(st+dr)/2;
        m=0;
        for(i=5;i<=mid;i+=5){
            n=i;
            while(n%5==0){
                m++;
                n=n/5;
            }
        }
        if(m==p){
            mid=mid-mid%5;
            fout<<mid;
            return 0;
        }
        else
            if(m>p)
                dr=mid-1;
            else
                st=mid+1;
    }
    fout<<-1;
}