#include <bits/stdc++.h>
// #include "homecoming.h"
using namespace std;
typedef long long ll;
ll solve(int n, int k, int *a, int *b){
ll dp[2 * n + 10] = {};
ll pa[2 * n + 10], pb[2 * n + 10];
pa[0] = pb[0] = 0;
for (int i = 1; i <= 2 * n; i ++){
pa[i] = pa[i - 1] + a[(i - 1) % n];
pb[i] = pb[i - 1] + b[(i - 1) % n];
}
ll ans = pa[n] - pb[n];
for (int i = 1; i <= n; i ++){
memset(dp, 0, sizeof dp);
ll mx = -1e18;
for (int j = i + 1; j < i + n; j ++){
dp[j] = dp[j - 1];
ans = max(ans, dp[j]);
if (j - k < i) continue;
mx = max(mx, dp[j - k] - pa[j - k] + pb[j - k]);
ll val = pa[j - k + 1] - pb[j];
dp[j] = max(dp[j], mx + val);
ans = max(ans, dp[j]);
}
}
ans = max(ans, 0ll);
return ans;
}
// int main(){
// int n = 5, k = 3;
// int a[n] = {10, 6, 2, 1, 1};
// int b[n] = {4, 3, 5, 2, 10};
// cout << solve(n, k, a, b) << endl;
// }
