KSum2

#include <bits/stdc++.h>
#include <cstdio>
#include <cstdlib>
#define maxn 100001
using namespace std;
FILE * fin=fopen("ksum2.in", "r+");
ofstream fout("ksum2.out");
vector<int> arr;
int N, K, W, pre[100001];

#define DIM 10000
char buff[DIM];
int poz=0;

void citeste(int &numar)
{
     numar = 0;
     char semn='+';
     while (buff[poz] < '0' || buff[poz] > '9')
     {
          semn = buff[poz];
          if (++poz == DIM)
               fread(buff,1,DIM,fin),poz=0;
     }
     while ('0'<=buff[poz] && buff[poz]<='9')
     {
          numar = numar*10 + buff[poz] - '0';
          if (++poz == DIM)
               fread(buff,1,DIM,fin),poz=0;
     }
     if (semn == '-')
          numar = -numar;
}

int main()
{
    int x;
    citeste(N);
    citeste(K);
    citeste(W);
    citeste(x);
    arr.push_back(x);
    pre[0]=x;
    for(int i=1; i<N; ++i)
    {
        citeste(x);
        arr.push_back(x);
        pre[i] = pre[i - 1] + arr[i];
    }
    multiset<int> s1;
    s1.insert(0);
    int ans = INT_MIN;
    ans = max(ans, pre[K - 1]);
    int flag = 0;
    for (int i = K; i < N; i++)
    {
        if (i - W >= 0)
        {
            if (flag == 0)
            {

                auto it = s1.find(0);
                s1.erase(it);
                flag = 1;
            }
        }
        if (i - K >= 0)
            s1.insert(pre[i - K]);
        ans = max(ans, pre[i] - *s1.begin());
        if(i - W >= 0)
        {
            auto it = s1.find(pre[i - W]);
            s1.erase(it);
        }
    }
    fout<<ans;
    return 0;
}