for _ in range(int(input())):
    n = int(input())
    d = {}
    m = 0
    for _ in range(n):
        x, y = map(int, input().split())
        d[x] = y
        if x > m:
            m = x
            
    p = d.get(0, 0)
    ans = m
    x = 1
    while p > 0:
        ans = max(ans, x)
        cx = d.get(x, 0)
        if p > cx:
            p = (p + cx) // 2
        else:
            p = p  
        x += 1
        
    print(ans)