from bisect import bisect_left
from collections import deque
N,M = map(int,input().split())
S = list(map(int,input().split()))
S = sorted(S)
T = list(map(int,input().split()))
ans = 0
high = M+1
low = 0
while high-low>1:
    mid = (high+low)//2
    T1 = sorted(T[:mid])
    S1 = deque(S[:])
    a = 0
    flag = True
    for i in range(mid):
        x = T1[i]
        ind = bisect_left(S1,x)
        if ind==len(S1):
            flag = False
            break
        else:
            a = max(a,abs(S1[ind]-x))
            for j in range(ind+1):
                S1.popleft()
    if flag:
        ans = a
        low = mid
    else:
        high = mid
print(ans)