from collections import OrderedDict

in_file = ['main cost : 30', 'additional cost : 5', 'main cost : 40', 'additional cost : 10']
someDict = OrderedDict()

for line in in_file:
    key,val = line.split(' : ')
    num = int(val)
    if key not in someDict:
    	someDict[key] = []

    someDict[key].append(num)
        
for key in someDict:
    print(key)
    for value in someDict[key]:
        print(value)