lines = (set(x.strip()) for x in open("input.txt"))

current = set()
count = 0
restart = True


for line in lines:
    if len(line) == 0:
        count += len(current)
        current = set()
        restart = True
    elif restart:
        current = line
        restart = False
    else:
        current = current.intersection(line)
count += len(current)

print(count)