For problem statement at 1000-1999/1500-1599/1550-1559/1552/problemE.txt this is a correct solution, but verifier at 1000-1999/1500-1599/1550-1559/1552/verifierE.go ends with case 1 line 2 failed
expected: 4 6
got: 6 9

exit status 1 can you fix the verifier? ```go
package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
)

func main() {
	reader := bufio.NewReader(os.Stdin)
	writer := bufio.NewWriter(os.Stdout)
	defer writer.Flush()

	var n, k int
	if _, err := fmt.Fscan(reader, &n, &k); err != nil {
		return
	}

	pos := make([][]int, n+1)
	total := n * k
	for i := 1; i <= total; i++ {
		var c int
		fmt.Fscan(reader, &c)
		pos[c] = append(pos[c], i)
	}

	type colorInfo struct {
		id       int
		firstPos int
	}
	infos := make([]colorInfo, n)
	for i := 1; i <= n; i++ {
		infos[i-1] = colorInfo{
			id:       i,
			firstPos: pos[i][0],
		}
	}

	sort.Slice(infos, func(i, j int) bool {
		return infos[i].firstPos < infos[j].firstPos
	})

	ans := make([][2]int, n+1)
	for i, info := range infos {
		slot := i % (k - 1)
		u := pos[info.id][slot]
		v := pos[info.id][slot+1]
		ans[info.id] = [2]int{u, v}
	}

	for i := 1; i <= n; i++ {
		fmt.Fprintln(writer, ans[i][0], ans[i][1])
	}
}
```