#include <iostream>
#include <bits/stdc++.h>
using namespace std;
#define ll long long int
vector<ll> a;
bool pp(ll n){
    if(n<=1) return false;
    else if(n==2 || n==3) return true;
    else if(n%2==0 || n%3==0) return false;
    else{
        for(ll i=5;i*i<=n;i+=6){
            if(n%i==0 || n%(i+2)==0) return false;
            
        }
        return true;
    }
}
int main() {
    ll n;
    cin>>n;
    ll ans=0;
    for(ll i=1;i<=n;i++){
        if(!pp(i)) a.push_back(i);
    }
    sort(a.begin(),a.end());
    cout<<a[0]<<endl;
    return 0;
}