#include<iostream>
#include<stdio.h>
using namespace std;
int main(){
    int l1,l2,p,m,c,fac,poz,i,ci;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    cin>>p;
    l1=1;
    l2=100000001;
    while(l1<=l2){
        m=(l1+l2)/2;
        c=0;
        for(i=5;i<=m;i+=5){
            ci=i;
            while(ci!=0&&ci%5==0){
                ci=ci/5;
                c++;
            }
        }
        if(c<p)
            l1=m+1;
        if(c>p)
            l2=m-1;
        if(c==p){
            poz=m;
            l2=m-1;
        }
    }
    cout<<poz;
    return 0;
}