#include <bits/stdc++.h>
#include "homecoming.h"
using namespace std;
long long solve(int n, int k, int *a, int *b){
long long cur, cost, nextcost, maxi = INT_MIN, maxj = INT_MIN;
cost = accumulate(b, b + k, 0ll);
maxi = a[0] - cost;
cur = a[0] - cost;
for(int i = 1; i < n; i++){
cost -= b[i - 1];
if(i + k - 1 < n) nextcost = b[k + i - 1];
else nextcost = 0;
cur = max(cur + a[i] - nextcost, maxi + a[i] - (cost + nextcost));
maxi = max(maxi, cur);
cost += nextcost;
}
cost = accumulate(b, b + k, 0ll);
maxj = max(0ll, a[0] - cost);
cur = a[0] - cost;
for(int i = 1; i < n; i++){
cost -= b[i - 1];
if(i + k - 1 < n) nextcost = b[k + i - 1];
else nextcost = b[k + i - 1 - n];
cur = max(cur + a[i] - nextcost, maxj + a[i] - (cost + nextcost));
maxj = max(maxj, cur);
cost += nextcost;
}
maxi = max(maxi, maxj);
return maxi;
}
