rt,调来调去就是WA在Subtask2第一个点

#include <bits/stdc++.h>

#define endl '\n'

using namespace std;

const int N = 5 * 1e5 + 5;

int n;
int a[N], b[N];
int ans = - 1;

signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
	cin >> n;
	for(int i = 1; i <= n; i ++) {
		cin >> a[i] >> b[i];
	}
	for(int i = 1; i < n; i ++) {
		if(a[i]+b[i]<a[i+1]) {
			ans = max(ans, a[i+1]-(a[i]+b[i]));
		}
	}
	cout << ans << endl;
    return 0;
}