Use a set or a boolean array to avoid double-counting duplicates.

Here is some java code:

    
    /**
     * Do it!
     */
    private void doit()
    {
        int n = sc.nextInt();
        int k = sc.nextInt();
        
        int count = 0;
        boolean used[] = new boolean[51];
        Arrays.fill( used, false );
        
        for( int i=0; i<n; i++ )
        {
            int d = sc.nextInt();
            if( !used[d] ) ++count;
            used[d] = true;
        }
        
        ps.println( Math.min( k, count ) );
    }