import sys

for line in sys.stdin:
    a = line.split("\n")[0].split(",...,")
    a1,a2 = a[0].split(",")[1],a[1]
    #print(a1,a2)
    print(int(a2)-int(a1)-1)

切割一下就行。没那种第一个为空或者多个。。。的情况