import std.stdio, std.array, std.string, std.conv, std.algorithm;
import std.typecons, std.range, std.random, std.math, std.container;
import std.numeric, std.bigint, core.bitop, core.stdc.stdio;

void main() {
    auto s = readln.split.map!(to!int);
    auto n = s[0];
    auto k = s[1] - 1;
    auto X = readln.split.map!(to!long).array;
    auto A = readln.split.map!(to!long).array;

    auto B = n.iota.map!(i => tuple(X[i], A[i], i)).array;
    B.sort!"a[0] < b[0]";

    int idx = -1;
    foreach (i; 0..n) if (B[i][2] == k) idx = i;

    int ans = 1;
    long mx = B[idx][0] + B[idx][1];

    foreach (i; idx+1..n) {
        if (B[i][0] <= mx) {
            ans += 1;
            mx = max(mx, B[i][0] + B[i][1]);
        }
    }

    mx = B[idx][0] - B[idx][1];

    foreach_reverse (i; 0..idx) {
        if (B[i][0] >= mx) {
            ans += 1;
            mx = min(mx, B[i][0] - B[i][1]);
        }
    }

    ans.writeln;
}