#include <bits/stdc++.h>
#include "homecoming.h"
using namespace std;
const long long INF = 1e18;
long long solve(int n, int k, int *a, int *b){
long long ans = 0;
long long mx, cur, cost, nxtcost;
for(int it = 1; it <= 2; it++){
mx = (it == 1 ? -INF : 0);
cost = accumulate(b, b + k, 0ll);
cur = a[0] - cost;
mx = max(mx, cur);
for(int i = 1; i < n; i++){
cost -= b[i - 1];
if(i + k - 1 < n) nxtcost = b[i + k - 1];
else if(it == 2) nxtcost = b[i + k - 1 - n];
else nxtcost = 0;
cur = max(a[i] + cur - nxtcost, a[i] - (cost + nxtcost) + mx);
cost += nxtcost;
mx = max(mx, cur);
}
ans = max(ans, mx);
}
return ans;
}
