input (5050B)
1Step S must be finished before step V can begin. 2Step J must be finished before step T can begin. 3Step N must be finished before step Q can begin. 4Step O must be finished before step H can begin. 5Step I must be finished before step C can begin. 6Step Y must be finished before step R can begin. 7Step K must be finished before step B can begin. 8Step A must be finished before step C can begin. 9Step B must be finished before step D can begin. 10Step W must be finished before step T can begin. 11Step E must be finished before step V can begin. 12Step Q must be finished before step L can begin. 13Step U must be finished before step P can begin. 14Step R must be finished before step C can begin. 15Step V must be finished before step M can begin. 16Step X must be finished before step P can begin. 17Step G must be finished before step T can begin. 18Step T must be finished before step Z can begin. 19Step Z must be finished before step M can begin. 20Step F must be finished before step C can begin. 21Step M must be finished before step L can begin. 22Step D must be finished before step C can begin. 23Step H must be finished before step L can begin. 24Step L must be finished before step P can begin. 25Step P must be finished before step C can begin. 26Step S must be finished before step Q can begin. 27Step M must be finished before step P can begin. 28Step S must be finished before step T can begin. 29Step U must be finished before step T can begin. 30Step X must be finished before step H can begin. 31Step Q must be finished before step G can begin. 32Step Y must be finished before step U can begin. 33Step H must be finished before step C can begin. 34Step O must be finished before step F can begin. 35Step S must be finished before step P can begin. 36Step B must be finished before step E can begin. 37Step S must be finished before step D can begin. 38Step R must be finished before step X can begin. 39Step Z must be finished before step D can begin. 40Step J must be finished before step C can begin. 41Step Z must be finished before step F can begin. 42Step K must be finished before step T can begin. 43Step T must be finished before step H can begin. 44Step E must be finished before step H can begin. 45Step D must be finished before step L can begin. 46Step O must be finished before step A can begin. 47Step V must be finished before step T can begin. 48Step V must be finished before step X can begin. 49Step Q must be finished before step X can begin. 50Step O must be finished before step K can begin. 51Step L must be finished before step C can begin. 52Step W must be finished before step H can begin. 53Step I must be finished before step T can begin. 54Step M must be finished before step H can begin. 55Step V must be finished before step G can begin. 56Step K must be finished before step P can begin. 57Step E must be finished before step X can begin. 58Step V must be finished before step C can begin. 59Step Y must be finished before step W can begin. 60Step J must be finished before step G can begin. 61Step B must be finished before step C can begin. 62Step B must be finished before step Z can begin. 63Step K must be finished before step R can begin. 64Step Y must be finished before step V can begin. 65Step X must be finished before step G can begin. 66Step J must be finished before step K can begin. 67Step A must be finished before step M can begin. 68Step T must be finished before step M can begin. 69Step W must be finished before step D can begin. 70Step G must be finished before step F can begin. 71Step A must be finished before step B can begin. 72Step W must be finished before step F can begin. 73Step Y must be finished before step P can begin. 74Step B must be finished before step V can begin. 75Step N must be finished before step G can begin. 76Step J must be finished before step H can begin. 77Step S must be finished before step L can begin. 78Step A must be finished before step R can begin. 79Step X must be finished before step D can begin. 80Step Y must be finished before step M can begin. 81Step H must be finished before step P can begin. 82Step F must be finished before step D can begin. 83Step S must be finished before step G can begin. 84Step K must be finished before step C can begin. 85Step W must be finished before step Z can begin. 86Step A must be finished before step Z can begin. 87Step O must be finished before step Y can begin. 88Step U must be finished before step C can begin. 89Step X must be finished before step M can begin. 90Step Y must be finished before step A can begin. 91Step F must be finished before step P can begin. 92Step J must be finished before step Y can begin. 93Step R must be finished before step G can begin. 94Step Y must be finished before step Q can begin. 95Step D must be finished before step P can begin. 96Step O must be finished before step U can begin. 97Step O must be finished before step I can begin. 98Step E must be finished before step L can begin. 99Step G must be finished before step Z can begin. 100Step T must be finished before step F can begin. 101Step Q must be finished before step F can begin.