def solve():
    N = int(input())
    T = list(map(int, input().split()))
    s = list(map(int, input().split()))

    ans = 0
    u = 0
    for i in range(N):
        if u <= s[i]:
            ans += 1
            u = s[i] + T[i]
    return ans

#==================================================
print(solve())