For problem statement at 0-999/600-699/630-639/635/problemA.txt this is a correct solution, but verifier at 0-999/600-699/630-639/635/verifierA.go ends with All tests passed can you fix the verifier? package main

import (
	"fmt"
)

func main() {
	var r, c, n, k int
	if _, err := fmt.Scan(&r, &c, &n, &k); err != nil {
		return
	}

	x := make([]int, n)
	y := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&x[i], &y[i])
	}

	ans := 0
	for r1 := 1; r1 <= r; r1++ {
		for r2 := r1; r2 <= r; r2++ {
			for c1 := 1; c1 <= c; c1++ {
				for c2 := c1; c2 <= c; c2++ {
					cnt := 0
					for i := 0; i < n; i++ {
						if x[i] >= r1 && x[i] <= r2 && y[i] >= c1 && y[i] <= c2 {
							cnt++
						}
					}
					if cnt >= k {
						ans++
					}
				}
			}
		}
	}
	fmt.Println(ans)
}