#include "hack.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define ff first
#define ss second
#define all(s) s.begin(),s.end()
#define rall(s) s.rbegin(),s.rend()
const ll N=1e6,inf=(ll)1e18;
vector<ll>prime;
bool run=false;
vector<ll>g[N+5];
vector<bool>ck(N+5,true);
// collisions
int hack(){
if(!run){
run=true;
for(ll i=1;i<=N;i++){
g[N/i*i].pb(i);
}
}
vector<ll>v={1,1};
for(ll i=N;i>N/2;i--){
v[1]=i+1;
if(collisions(v)==1){
ll ans=i;
for(ll j=0;j<(ll)g[i].size()-1;j++){
v[1]=g[i][j]+1;
if(collisions(v)==1){
ans=g[i][j];
break;
}
}
return ans;
}
}
return 0;
}
