Go: package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
)

func main() {
	parseProblem(os.Stdin)
}

func parseProblem(r io.Reader) {
	const (
		initialBufSize = 100000
		maxBufSize     = 1000000
	)
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	for true {
		n, k := scanInt(sc), scanInt(sc)
		if n == 0 && k == 0 {
			break
		}
		sum := make([]int, n+2)
		for i := 2; i <= n+1; i++ {
			sum[i] = sum[i-1] + scanInt(sc)
		}
		max := math.MinInt32
		for i := 1; i+k <= n+1; i++ {
			if v := sum[i+k] - sum[i]; max < v {
				max = v
			}
		}
		fmt.Println(max)
	}
	return
}

func resolve(n int) int {
	return n
}

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: #include<bits/stdc++.h>
using namespace std;

template<class T>
struct treap{
    #define treapInf INT_MAX

public:
    struct node{
        T val;
        node *lch,*rch;
        int pri,sz;
        T sum,mini;

        node(T val,int pri):val(val),pri(pri),sz(1),sum(val),mini(val){
            lch=rch=NULL;
        }
    };

    node *root;
    treap():root(NULL){srand(time(NULL));}

private:

    inline int size(node *t){return !t?0:t->sz;}
    inline T sum(node *t){return !t?0:t->sum;}
    inline T mini(node *t){return !t?treapInf:t->mini;}

    node *update(node *t){
        if(!t)return t;
        t->sz=size(t->lch)+size(t->rch)+1;
        t->sum=sum(t->lch)+sum(t->rch)+t->val;
        t->mini=min(min(mini(t->lch),mini(t->rch)),t->val);
        return t;
    }

    node *merge(node *l,node *r){
        if(!l||!r)return l?l:r;

        if(l->pri>r->pri){
            l->rch=merge(l->rch,r);
            return update(l);
        }
        else{
            r->lch=merge(l,r->lch);
            return update(r);
        }
    }

    pair<node *,node *>split(node *t,int k){
        if(!t)return make_pair((node *)NULL,(node *)NULL);

        if(k<=size(t->lch)){
            pair<node *,node *>s=split(t->lch,k);
            t->lch=s.second;
            return make_pair(s.first,update(t));
        }
        else{
            pair<node *,node *>s=split(t->rch,k-size(t->lch)-1);
            t->rch=s.first;
            return make_pair(update(t),s.second);
        }
    }

    node *insert(node *t,int k,T val,int pri){
        pair<node *,node *>s=split(t,k);
        t=merge(s.first,new node(val,pri));
        t=merge(t,s.second);
        return update(t);
    }

    node *erase(node *t,int k){
        pair<node *,node *>s1,s2;
        s2=split(t,k+1);
        s1=split(s2.first,k);
        return update(t=merge(s1.first,s2.second));
    }

    node *find(node *t,int k){
        //if(!t)return t;
        int c=size(t->lch);
        if(k<c)return find(t->lch,k);
        if(k==c)return t;
        return find(t->rch,k-c-1);
    }

    T rangeMinimumQuery(int l,int r,node *t){
        int sz=size(t);
        if(r<=0||sz<=l)return treapInf;
        if(l<=0&&sz<=r)return mini(t);

        sz=size(t->lch);
        T vl=rangeMinimumQuery(l,r,t->lch);
        T vr=rangeMinimumQuery(l-sz-1,r-sz-1,t->rch);
        T res=min(vl,vr);
        if(l<=sz&&sz<r)res=min(res,t->val);
        return res;
    }

    T rangeSumQuery(int l,int r,node *t){
        int sz=size(t);
        if(r<=0||sz<=l)return 0;
        if(l<=0&&sz<=r)return sum(t);

        sz=size(t->lch);
        T vl=rangeSumQuery(l,r,t->lch);
        T vr=rangeSumQuery(l-sz-1,r-sz-1,t->rch);
        T res=vl+vr;
        if(l<=sz&&sz<r)res+=t->val;
        return res;
    }

    void debug(node *t){
        if(!t)return;
        debug(t->lch);
        cout<<t->val<<" ";
        debug(t->rch);
    }

public:

    void insert(int k,T val){root=insert(root,k,val,rand());}
    void erase(int k){root=erase(root,k);}
    node *find(int k){return find(root,k);}

    void add(int k,T v){
        node *a=find(k);
        T tmp=a->val;
        erase(k);
        insert(k,tmp+v);
    }

    void update(int k,T v){
        erase(k);
        insert(k,v);
    }

    T rangeMinimumQuery(int l,int r){
        return rangeMinimumQuery(l,r,root);
  }


    T rangeSumQuery(int l,int r){
        return rangeSumQuery(l,r,root);
    }

    void init(int n,T val){
        for(int i=0;i<n;i++)insert(i,val);
    }

    void debug(){
        debug(root);
        cout<<endl;
    }
};


int main(){

    int N,K;
    while(cin>>N>>K){
        treap<long long>t;
        for(int i=0;i<N;i++){
            int a;cin>>a;
            t.insert(i,a);
        }

        long long ma=LLONG_MIN;

        for(int i=0;i+K<=N;i++){
            ma=max(ma,t.rangeSumQuery(i,i+K));
        }

        cout<<ma<<endl;
    }
    return 0;
}

C++: #include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    int i, n, k;
    cin >> n >> k;
    int a[n];
    for(i=0; i<n ;i++){
        cin >> a[i];
    }
    int max_val;
    int S;
    //--init--
    S = 0;
    for(i=0; i<k; i++){
        S += a[i];
    }
    max_val = S;
    for(i=0; i<n-k; i++){
        S += a[i+k];
        S -= a[i];
        if(max_val < S){
            max_val = S;
        }
    }
 
    std::cout << max_val << std::endl;
    return 0;
}

C++: #include <iostream>
using namespace std;
int main(void){
	for (;;){
	int a,b,c[100000]={0},d=0,e=0,max=0;
			cin>>a>>b;
			if (a==0&&b==0)break;
			for (int A=0;A<a;A++){
			cin>>c[A];
			if (A>=b){
				for (int B=0;B<b;B++){
					d=d+c[A+e];
					e--;
				}
				if (max<d)max=d;
				d=0;
				e=0;
			}
		}
		cout<<max<<endl;
	}
	return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <map>

using namespace std;

typedef long long ll;

int a[100000] = {};

signed main() {
	int k;
	int n;
	
	while (true) {
		cin >> n >> k;
		if (n == 0 && k == 0) return 0;
			for (int i = 0; i < n; i++) {
				cin >> a[i];
			}

			int m = -9999999999;
			int tmp = 0;
			int cnt = 0;

			for (int i = 0; i < n; i++) {
				if (i < k) {
					tmp += a[i];
				}
				else {
					tmp -= a[i - k];
					tmp += a[i];
					m = max(m, tmp);
				}
			}

			cout << m << endl;
		
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int main()
{
    int n,m,result;
    int num[100005];
    int memo[100000];
    while(1)
    {
        cin >> n >> m;
        if(n == 0 && m == 0)break;
        for(int i = 0; i < n; i++)cin >> num[i];
        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                memo[i] = num[m-j];
            }
        }
        for(int i = 0; i < n; i++)
        {
            result = max(result,memo[i]);
        }
        cout << result << endl;
    }
    return 0;
}

C++: #include <iostream>
using namespace std;

int n;
int a[100000];

int main() {
	cin >> n;

	static int ra[100001];	//ra[i] = a[0] + ??? + a[i-1]
	ra[0] = 0;
	for (int i = 0; i < n; i++) {
		ra[i+1] = ra[i] + a[i];
	}

	int ans = -1000000001;
	for (int i = 0; i < n - k; i++) {
		//a[i] + ??? + a[i+k-1]
		ans = max(ans, ra[i+k] - ra[i]);
	}

	cout << ans << endl;
	return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int n=0, k=0;
double a[100001] = {}, b[100001] = {}, ans=0;
int main(){
	while (true){
		n = 0; k = 0;
		ans = 0;
		cin >> n >> k;
		if (n == 0 || k == 0)	break;
		for (int i = 1; i <= n; i++){
			cin >> a[i];
		}
		for (int x = 0; x<k; x++){
			b[1] += a[x+1];
		}
		for (int i = 2; i <= n; i++){
			if (a[i + k - 1] == 0)	break;
			b[i] = b[i - 1] - a[i - 1] + a[i + k - 1];
				ans = max(b[i],b[i-1]);
			}
		cout << ans << endl;
		}	
	return 0;
}