#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vl vector<ll>
#define vvl vector<vl>
template<class T> inline int chmax(T &a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline int chmin(T &a, T b) { if (a > b) { a = b; return 1; } return 0; }
auto _ = []() { ios::sync_with_stdio(false); cin.tie(nullptr); return 0; }();

int main() {
  
  ll N, M; cin >> N >> M;
  
  vl A(N), B(N);
  
  for (auto& x : A) cin >> x; for (auto& x : B) cin >> x;
  
  ll ma = 0;
  
  for (int s = 0; s <= N - M; s++) {
    
    ll cur = 0;
    
    for (int i = 0; i < M; i++) cur += max(0LL, A[s + i] - B[s + i]);
    
    chmax(ma, cur);
    
  }
  
  cout << ma << "\n";
  
  return 0;
  
}