题解 | 诗

package main

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

func main() {
	reader := bufio.NewReader(os.Stdin)
	var str string
	fmt.Fscan(reader, &str)
	runes := []rune(str)
	//fmt.Println(string(runes))
	result := make([]rune, 0)
	index := 0
    n:=len(runes)
	for i := 0; index+i < n; i++ {
		index += i
		result = append(result, runes[index])
		
	}
	fmt.Println(string(result))
}