Wrong Answer.wrong answer 1st numbers differ - expected: '1000', found: '500000500'

#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define rep(i,x,y) for(ll i=x;i<=y;i++)
#define pll pair<ll,ll>
#define pause system("pause")
#define IL inline

const ll N=2e5+10,MAX=1e9+1000,S=41;
ll n,goal,st[N],t[N],pow2[S];
bool done;

void bs(ll l,ll r) {
	if(done or l>r) return;

//	cout<<l<<' '<<r<<'\n';
	ll mid=l+r>>1ll,ans=0;

//	if(mid>goal) {
//		bs(l,mid-1);
//		return;
//	}

	rep(i,1,n) {
		if(mid>=st[i]+t[i]) {
			ll tt=mid-t[i]-st[i]+1ll;

			if(tt<S and tt<goal and pow2[tt]<=goal) ans+=pow2[tt];
			else {
				bs(l,mid-1ll);
				return;
			}
		} else if(mid>=st[i]) ans++;

		if(ans>goal) {
			bs(l,mid-1ll);
			return;
		}
	}

//	if(mid==5) {
//		cout<<"mid="<<mid<<'\n'<<"ans="<<ans;
//		pause;
//	}

	if(ans==goal) {
		cout<<mid;
		done=1;
		return;
	}

	bs(mid+1ll,r);
}

int main() {
	pow2[0]=1ll;

	rep(i,1,S-1) pow2[i]=pow2[i-1]<<1ll;

//	rep(i,0,S-1) cout<<pow2[i]<<' ';
//
//	pause;
	cin>>n>>goal;

	rep(i,1,n) cin>>st[i];

	rep(i,1,n) cin>>t[i];

	bs(1,MAX);
	
	if(done==0) cout<<"-1";
}