#include <bits/stdc++.h>   using namespace std;   const long long N = 1e5 + 10;   const long long M = 998244353;   const long double PI = acos(-1);   long long n, k;   long long a[N], d[N], mn[N] = {INT_MAX};   signed main() {     long long i, s = 0, ans = 0;     cin >> n >> k;     for (i = 1; i <= n; i++) cin >> a[i];     for (i = 1; i <= n; i++) cin >> d[i], mn[i] = min(mn[i - 1], d[i]);     for (i = n; i >= 1; i--) a[i] += a[i + 1];     if (k == 0) {       for (i = 1; i <= n; i++) ans = max(ans, a[i] - d[i]);       cout << ans;     } else if (k == 1) {       for (i = 2; i <= n; i++)         ans = max(ans, max(0ll, a[1] - a[i] - mn[i - 1]) + max(0ll, a[i] - d[i]));       for (i = 1; i < n; i++)         ans = max(ans, a[1] - (a[i + 1] - a[i + 2]) - d[1] +                            max(0ll, a[i + 1] - a[i + 2] - d[i + 1]));       cout << ans;     } else       cout << max({0ll, a[1] - mn[n - 1], a[n] - d[n]});     return 0;   }   