Problem Statement

Yuki-kun has forgotten the PIN of his bicycle lock. Tell Yuki-kun some numbers and help him somehow unlock it.

The PIN is a 3-digit number (000 to 999). When you print a 3-digit number (including leading zeros) to standard output, the judge returns one of the strings "locked" or "unlocked" to standard input.
When "locked" is returned, the lock has not been unlocked yet. Try another number.
When "unlocked" is returned, the lock has been unlocked. Terminate your program. Any extra output after the query that unlocked the lock results in WA.
You may try as many times as you like within the time limit.

Input and Output

This problem is a reactive problem. Perform input and output operations according to the problem statement. In particular, do not forget to end each output with a newline and flush it.
For notes on input and output in reactive problems, see the summary of reactive problems on the yukicoder wiki, as well as No.246, No.253, and others.

Judge Code (for reference)

This is the code used for judging. (C++; it reads the answer string from the file given as the first command-line argument.)
2016/05/04: The judge code has been changed. Invalid formats (such as output other than digits), multiple outputs on one line, and extra output after unlocking result in WA.

#include <iostream>
#include <fstream>
#include <cassert>
using namespace std;

string input(istream& is){
    string ret;
    getline(is, ret);         //回答コードから受け取った文字列
    assert(ret.size() == 3);  //長さは 3
    for(char c : ret){        //数字のみかチェック
        assert('0' <= c && c <= '9');
    }
    return ret;
}

int main(int argc, char* argv[]){
    ifstream ifs(argv[1]);
    string ans = input(ifs);     //第一引数のファイルから正解の文字列を取得
    cerr << "Answer : " << ans << endl;

    while(1){
        string in = input(cin);  //標準入力から回答の文字列を取得
        if(in == ans){           //正解なら "unlocked" を出力して終了
            cout << "unlocked" << endl;
            if(getline(cin,in)){  //余計な出力がないか確認
                cerr << "Wrong Answer : too many outputs, \"" << in << "\"" << endl;
                abort();
            }
            return 0;
        }else{                   //不正解なら "locked" を出力
            cout << "locked" << endl;
        }
    }
    return 0;
}

Sample

000

003
002
001
000

locked
locked
locked
unlocked

123

120
121
122
123

locked
locked
locked
unlocked