#include<bits/stdc++.h>
#define REP(i,n) for(int i=0,i##_len=(n);i<i##_len;++i)
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define All(x) (x).begin(),(x).end()
using namespace std;

int main(){
    typedef long long ll;
    int N, K; cin >> N >> K;
    vector<ll> X(N), A(N);
    REP(i, N) cin >> X[i];
    REP(i, N) cin >> A[i];
    K--;
    ll l = X[K] - A[K];
    ll r = X[K] + A[K];
    int res = 0;
    int a = K, b = K;
    while (res<N) {
        int ld = lower_bound(All(X), l) - X.begin();
        int rd = upper_bound(All(X), r) - X.begin();
    
        for (int i = ld; i < a; ++i) {
            l = min(l, X[i] - A[i]);
            r = max(r, X[i] + A[i]);
        }
        for (int i = b+1; i < rd; ++i) {
            l = min(l, X[i] - A[i]);
            r = max(r, X[i] + A[i]);
        }
        int tmp=res;
        res = rd - ld + 1;
        if(res==tmp) break;
        a = ld, b = rd;
    }
    cout << res << endl;
    return 0;
}