Programs are free to participate in one or both.
The stronger program can win as white with 0 stones handicap and 0.5 komi, but not when giving 2 stones handicap with 0.5 komi. The stronger program has not played the weaker program. A ladder participant may challenge the program above to attempt to decrease the number of stones, or the program below to increase the number of stones. In the case where the difference to the program above is 0 stones, the programs would exchange places on the ladder if the challenge were successful. Then handicap challenges would be played to determine the new program's exact position.