import java.util.regex.Pattern;
 
class Ideone
{
    static Pattern pattern = Pattern.compile("[a-zA-Z0-9]{0,100}(?:(?:<a>[a-zA-Z0-9]{0,100}(?:<b>[a-zA-Z0-9]{0,100}</b>[a-zA-Z0-9]{0,100})?</a>|<b>[a-zA-Z0-9]{0,100}</b>)[a-zA-Z0-9]{0,100})*");
    static void test(String s)
    {
        System.out.println(s);
        System.out.println(pattern.matcher(s).matches() ? 1 : 0);
    }
 
    public static void main(String[] args)
    {
        test("<a>ruby<b>php</b>python</a><a><b></b></a><a></a>");
        test("<a>ruby<b>php</b>python</a><a></b></a><a></a>");
        test("<a>ruby<b>php</b>python</a><a><b></a><a></a>");
        test("<a>ruby<b>php</b>python</a><a><b></b></a><a>");
        test("vvvc<a>ruby<b>php</b>python</a><a><b></b></a><a></a>");
    }
}

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