#!/usr/bin/env python3
import sys

def main():
    from collections import deque
    INF = 10 ** 16
    def bfs(edges: "List[to]", start_node: int) -> list:
        q = deque()
        dist = [INF] * len(edges)
        q.append(start_node)
        dist[start_node] = 0
        while q:
            now = q.popleft()
            for next in edges[now]:
                if dist[next] != INF:
                    continue
                q.append(next)
                dist[next] = dist[now] + 1
        return dist
    import bisect
    N, K = map(int, input().split())
    X = list(map(int, input().split()))
    A = list(map(int, input().split()))
    G = [[] for _ in range(N)]
    for i in range(N):
        l = bisect.bisect_left(X, X[i] - A[i])
        r = bisect.bisect_right(X, X[i] + A[i])
        for j in range(l, r):
            if i == j:
                continue
            G[i].append(j)
    d = bfs(G, K - 1)
    print(N - d.count(INF))
    return
        
if __name__ == '__main__':
    main()