线段的重叠

#include <bits/stdc++.h>
#define _xx ios_base::sync_with_stdio(0);cin.tie(0);
using namespace std;
typedef long long ll;
struct node
{
    int s, e;
} a[50005];
bool operator < (const node& t1, const node& t2)
{
    return t1.s < t2.s;
}
int main()
{_xx
    int n, ans = 0;
    cin >> n;
    for(int i = 1; i <= n; i++) cin >> a[i].s >> a[i].e;
    sort(a + 1, a + n + 1);
    int lmost = 0;
    for(int i = 1; i <= n; i++)
    {
        if(lmost <= a[i].e) ans = max(ans, lmost - a[i].s);
        else ans = max(ans, a[i].e - a[i].s);
        lmost = max(lmost, a[i].e);
    }
    cout << ans << endl;
    return 0;
}