KSum

#include <bits/stdc++.h>

using namespace std;
ifstream fin("ksum.in");
ofstream fout("ksum.out");
int n, k, a[100001], sum;

int main()
{
    fin>>n>>k;
    for(int i=0; i<n; ++i)
    {
        fin>>a[i];
        if(i<k)
            sum+=a[i];
    }
    int maxSum[n];
    maxSum[0] = a[0];
    int curr_max = a[0];
    for(int i = 1; i < n; i++)
    {
        curr_max = max(a[i], curr_max+a[i]);
        maxSum[i] = curr_max;
    }
    int result = sum;
    for (int i = k; i < n; i++)
    {
        sum = sum + a[i] - a[i-k];
        result = max(result, sum);
        result = max(result, sum + maxSum[i-k]);
    }
    fout<<result;
    return 0;
}