求助！

#include <iostream>
#include <algorithm>

using namespace std;

struct lqacn
{
    int x;
    int y;
}k[5005];

bool slk(lqacn a, lqacn b)
{
    return a.y < b.y;
}

int main()
{
    int n, s, t, g;
    cin >> n >> s >> t >> g;
    int h = t + g;
    for (int i = 1; i <= n; i++)
    {
        cin >> k[i].x >> k[i].y;
    }
    sort(k + 1, k + n + 1, slk);
    int ans = 0;
    for (int i = 1; i <= n; i++)
    {
        if(s > k[i].y && h > k[i].x) ans++;
    }
    cout << ans;
    return 0;
}