bzoj2006

#include<cstdio>
#include<cctype>
#include<queue>
#define maxn 500002
#define mp(a,b,c,d) make_pair(make_pair(a,b),make_pair(c,d))
using namespace std;
typedef pair<int,int>data;
priority_queue<pair<data,data> >q;
int n,m,l,r,logg[maxn],f[maxn][20],s[maxn],v[maxn];
long long ans;
inline void read(int &x){
    char ch=getchar();x=0;int f=1;
    while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
    while(isdigit(ch)){x=(x<<1)+(x<<3)+ch-‘0‘;ch=getchar();}
    x*=f;
}
inline int mn(int a,int b){return s[a]<s[b]?a:b;}
inline int query(int a,int b){if(a>b)return -1;int k=logg[b-a+1];return mn(f[a][k],f[b-(1<<k)+1][k]);}
int main(){
    int c,d,x,a,b,y;
    read(n);read(m);read(l);read(r);
    for(int i=2;i<=n;i++)logg[i]=logg[i>>1]+1;
    for(int i=1;i<=n;i++){f[i][0]=i;read(v[i]);s[i]=v[i]+s[i-1];}
    for(int j=1;(1<<j)<=n;j++)
       for(int i=0;i+(1<<j)<=n;i++)
          f[i][j]=mn(f[i][j-1],f[i+(1<<j-1)][j-1]);
    for(int i=l;i<=n;i++)q.push(mp(s[i]-s[query(max(i-r,0),i-l)],i,max(i-r,0),i-l));
    for(int i=1;i<=m;i++){
        data t1=q.top().first,t2=q.top().second;
        ans+=t1.first;x=t1.second;a=t2.first;b=t2.second;y=query(a,b);q.pop();
        c=query(a,y-1);d=query(y+1,b);
        if(c!=-1)q.push(mp(s[x]-s[c],x,a,y-1));
        if(d!=-1)q.push(mp(s[x]-s[d],x,y+1,b));
    }
    printf("%lld",ans);
    return 0;
}