This is true. But if you are clever, you can handle the case where you have 2 arbitrary integers whose sum is non-negative!
The trick is to zero out a counter, then increment it until it is one of the two starting values. Then start a second counter and increment it together with the other starting value until the second counter reaches the first and the other contains the sum of the two. Finally start a counter at location 2 and increment it until it reaches the value of the register that has the sum.
The trick is to zero out a counter, then increment it until it is one of the two starting values. Then start a second counter and increment it together with the other starting value until the second counter reaches the first and the other contains the sum of the two. Finally start a counter at location 2 and increment it until it reaches the value of the register that has the sum.