package main
 
import (
	"bufio"
	"fmt"
	"os"
)
 
func main() {
	scanner := bufio.NewScanner(os.Stdin)
 
	for scanner.Scan() {
		line := scanner.Text()
		if hasExactlyTwice(line) {
			fmt.Println(line)
		}
	}
 
	if err := scanner.Err(); err != nil {
		fmt.Println("read error:", err)
	}
}
 
func hasExactlyTwice(s string) bool {
	counter := make(map[rune]int)
	two := 0
 
	for _, ch := range s {
		counter[ch]++
		switch counter[ch] {
		case 2:
			two++
		case 3:
			two--
		}
	}
 
	return two > 0
}
 

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