#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

const int M=2e4+,inf=0x3f3f3f3f;

int read(){

    int ans=,f=,c=getchar();

    while(c<''||c>''){if(c=='-') f=-; c=getchar();}

    while(c>=''&&c<=''){ans=ans*+(c-''); c=getchar();}

    return ans*f;

}

int n,m,l,ans;

int sum[M],w[M],f[][M],mx;

int q[M],ql,qr,k;

int F(int x){return f[k-][x]-sum[x];}

int main(){

    freopen("hard.in","r",stdin);

    freopen("hard.out","w",stdout);

    n=read(); m=read(); l=read();

    for(int i=l;i<n+l;++i) w[i]=read();

    n=n+*l-;

    for(int i=;i<=n;++i) sum[i]=sum[i-]+w[i];

    for(int i=;i<l;++i) f[][i]=-inf;

    for(int i=l;i<=n;++i) f[][i]=sum[i]-sum[i-l];

    for(k=;k<=m;++k){

        ql=,qr=;

        mx=-inf;

        for(int i=;i<l;++i) f[k][i]=-inf;

        for(int i=l;i<=n;++i){

            while(ql<=qr&&q[ql]<=i-l) ++ql;

            while(ql<=qr&&F(q[qr])<=F(i-)) --qr;

            q[++qr]=i-;

            mx=max(mx,f[k-][i-l]);

            f[k][i]=max(mx+sum[i]-sum[i-l],F(q[ql])+sum[i]);

        }

    }

    ans=;

    for(int i=;i<=m;++i)

        for(int j=l;j<=n;++j) ans=max(ans,f[i][j]);

    printf("%d\n",ans);

    return ;

}