Codeforces #25 B "Phone numbers"

問題：http://codeforces.com/contest/25/problem/B

import java.util.Scanner;

public class B {
	public static void main(String[] args) throws Exception{
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		String s = scan.next();
		int a = s.length() % 2 < 1 ? 2 : 3;
		for(int i = 0; i < s.length() - a; i+=2){
			System.out.print(s.substring(i,i+2)+"-");
		}
		System.out.println(s.substring(s.length()-a,s.length()));
	}
	
}