第十七届中国计量大学程序设计竞赛 - C Cook Steak

for _ in range(int(input())):
    times = int(input())
    temper = 0
    for i in range(times):
        l, r = map(int, input().split())
        if temper > r:
            times = times + temper - r
            temper = r
        if temper < l:
            times = times + l - temper
            temper = l
    print(times)