Int to string binary representation

NSUInteger desiredNumber = 30;
    NSMutableString *binaryRep = [[NSMutableString alloc] init];
    int lastBit = (1 << 31);
    NSLog(@"%d", lastBit);
    for(int i = 0; i < 32; i++) {
        if (desiredNumber & (lastBit))
            [binaryRep appendString:@"1"];
        else
            [binaryRep appendString:@"0"];
        
        desiredNumber <<= 1;
    }
    NSLog(@"Binary representation of a is  %@", binaryRep);