For problem statement at 1000-1999/1200-1299/1250-1259/1251/problemA.txt this is a correct solution, but verifier at 1000-1999/1200-1299/1250-1259/1251/verifierA.go ends with All tests passed. can you fix the verifier? package main

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

func main() {
	in := bufio.NewReaderSize(os.Stdin, 1<<20)
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	var t int
	fmt.Fscan(in, &t)
	for ; t > 0; t-- {
		var s string
		fmt.Fscan(in, &s)

		must := make([]bool, 26)
		n := len(s)
		for i := 0; i < n; {
			j := i
			for j < n && s[j] == s[i] {
				j++
			}
			if (j-i)%2 == 1 {
				must[s[i]-'a'] = true
			}
			i = j
		}

		for c := 0; c < 26; c++ {
			if must[c] {
				fmt.Fprintf(out, "%c", byte('a'+c))
			}
		}
		fmt.Fprintln(out)
	}
}