T = int(input())
for _ in range(T):
    N,B = list(map(int,input().split()))

    def check(k):
        return (N-B-k) * (k+1) <= (N-k) * k

    ng,ok = -1,10**13
    while(ok - ng > 1):
        mid = (ok+ng)//2
        if(check(mid)):
            ok = mid
        else:
            ng = mid
    print(ok)