import java.util.Map;
import java.util.TreeMap;

class MultiSet
{
    private Map<String,Integer> counts;

    public MultiSet( )
    {
        counts = new TreeMap<String,Integer>( );
    }

    public String toString( )
    {
        return counts.toString( );
    }

    public int size( )
    {
        int total = 0;

        for( Integer occurs : counts.values( ) )
            total += occurs;

        return total;
    }

    public void add( String x )
    {
        Integer occurs = counts.get( x );

        if( occurs == null )
            counts.put( x, 1 );
        else
            counts.put( x, occurs + 1 );
    }

    // Remove an item.
    // If x is not found, return false.
    // If x is present with count 1, remove it from the map.
    // If x is present with count > 1, drop count
    public boolean remove( String x )
    {
        Integer occurs = counts.get( x );

        if( occurs == null )
            return false;

        if( occurs == 1 )
            counts.remove( x );
        else
            counts.put( x, occurs - 1 );

        return true;
    }

    public boolean contains( String x )
    {
        return counts.get( x ) != null;
    }

}

class Exam4
{
    public static void main( String [ ] args )
    {
        MultiSet m = new MultiSet( );

        m.add( "hello" );
        m.add( "world" );
        m.add( "zebra" );
        m.add( "hello" );

        System.out.println( m );
        System.out.println( m.contains( "hello" ) );
        System.out.println( m.contains( "oops" ) );
        System.out.println( m.size( ) );

        m.remove( "zebra" );
        m.remove( "hello" );
        System.out.println( m );

    }
}