int firstNumber = 1;
NSMutableString *numberList = [NSMutableString stringWithCapacity:5];
switch (firstNumber) {
    case 1:
    [numberList appendString: @"1"];
    case 2:
    [numberList appendString: @"-2"];
    case 3:
    [numberList appendString: @"-3"];
}
//numberList = "1-2-3"