#include<bits/stdc++.h>
#define forup(i,s,e) for(int i=(s),E123123123=(e);i<=E123123123;++i)
#define fordown(i,s,e) for(int i=(s),E123123123=(e);i>=E123123123;--i)
#define mem(a,b) memset(a,b,sizeof(a))
#ifdef DEBUG
#define msg(args...) fprintf(stderr,args)
#else
#define msg(...) void();
#endif
using namespace std;
using i64=long long;
using i128=__int128;
using pii=pair<int,i64>;
#define fi first
#define se second
#define mkp make_pair
#define gc getchar()
int read(){
    int x=0,f=1;char c;
    while(!isdigit(c=gc)) if(c=='-') f=-1;
    while(isdigit(c)){x=(x<<1)+(x<<3)+(c^48);c=gc;}
    return x*f;
}
#undef gc
const int N=2e5+5,B=1000,T=205;
i64 inf=1e18;
int n,m,a[N];
i64 sum[N];
int L[T],R[T],blg[N];
deque<pii> conv[T];
i128 cross(pii a,pii b){
    return a.fi*b.se-a.se*b.fi;
}
pii operator -(const pii a,const pii b){
    return mkp(a.fi-b.fi,a.se-b.se);
}
bool slp(pii a,pii b,pii c){
    return cross(b-a,c-b)<=0;
}
bool slp(pii a,pii b,i64 k){
    return (b.se-a.se)<(i128)(b.fi-a.fi)*k;
}
i64 dp[N];
int bkt[T][N],mex[T];
bool tag[T];
i64 mxv[T][N];
void work(int pl,int pr,int ql,int qr,int b){
    if(ql>qr) return;
    if(pl==pr){
        forup(i,ql,qr){
            mxv[b][i]=-sum[pl]*i+dp[pl];
        }
        return;
    }
    int mid=(ql+qr)>>1,p=0;
    i64 val=-inf;
    forup(i,pl,pr){
        if(-sum[i]*mid+dp[i]>val){
            p=i;
            val=-sum[i]*mid+dp[i];
        }
    }
    mxv[b][mid]=val;
    work(pl,p,mid+1,qr,b);work(p,pr,ql,mid-1,b);
}
void getconv(int j){
    deque<pii> &q=conv[j];
    q.clear();
    int mm=mex[j+1];
    vector<pii> vv;
    fordown(k,R[j],L[j]){
        while(bkt[j+1][mm]) ++mm;
        pii nw;
        nw.fi=mm;nw.se=mm*sum[k]-dp[k];
        vv.push_back(nw);
        ++bkt[j+1][a[k]];
    }
    forup(k,L[j],R[j]){
        --bkt[j+1][a[k]];
    }
    sort(vv.begin(),vv.end(),[&](pii a,pii b){if(a.fi!=b.fi)return a.fi<b.fi;return a.se<b.se;});
    for(auto i:vv){
        if(q.size()&&i.fi==q.back().fi) continue;
        while(q.size()>2&&slp(q[q.size()-2],q[q.size()-1],i)) q.pop_back();
        q.push_back(i);
    }
}
int bb[N],tt[N],m0;
signed main(){
    n=read();m=read();
    forup(i,1,n){
        a[i]=read();
        sum[i]=sum[i-1]+a[i];
    }
    int t=n/B;
    forup(i,1,t){
        L[i]=R[i-1]+1;R[i]=i*B;
        forup(j,L[i],R[i]) blg[j]=i;
    }
    if(R[t]!=n){
        ++t;
        L[t]=R[t-1]+1;R[t]=n;
        forup(j,L[t],R[t]) blg[j]=t;
    }
    forup(i,1,n){
        ++tt[a[i]];
        while(tt[m0]) ++m0;
        dp[i]=0;
        if(i<=m){
            dp[i]=max(dp[i],m0*sum[i]);
        }
        forup(j,1,t) tag[j]=0;
        fordown(j,blg[i],1){
            ++bkt[j][a[i]];
            while(bkt[j][mex[j]]) ++mex[j],tag[j]=1;
        }
        bb[a[i]]=1;
        int mm=0;
        fordown(j,i-1,max(L[blg[i]],i-m)){
            while(bb[mm]) ++mm;
            dp[i]=max(dp[i],dp[j]+mm*(sum[i]-sum[j]));
            bb[a[j]]=1;
        }
        fordown(j,i,max(L[blg[i]],i-m)){
            bb[a[j]]=0;
        }
        fordown(j,blg[i]-1,1){
            if(mex[j]!=mex[j+1]&&(tag[j]||tag[j+1])){
                getconv(j);
            }
        }
        if(i-m>=1&&blg[i]!=blg[i-m]){
            fordown(j,blg[i]-1,blg[i-m]+1){
                if(mex[j]==mex[j+1]){
                    dp[i]=max(dp[i],mex[j]*sum[i]+mxv[j][mex[j]]);
                    // msg("[%d]A %d %d %d %lld|%lld\n",i,L[j],R[j],mex[j],mxv[j][mex[j]],mex[j]*sum[i]+mxv[j][mex[j]]);
                }else{
                    while(conv[j].size()>=2&&slp(conv[j][0],conv[j][1],sum[i])) conv[j].pop_front();
                    dp[i]=max(dp[i],conv[j].front().fi*sum[i]-conv[j].front().se);
                    // msg("[%d]B %d %d %d %lld|%lld\n",i,L[j],R[j],conv[j].front().fi,-conv[j].front().se,conv[j].front().fi*sum[i]-conv[j].front().se);
                }
            }
            int mm=mex[blg[i-m]+1],p=blg[i-m]+1;;
            fordown(j,R[blg[i-m]],i-m){
                while(bkt[p][mm]) ++mm;
                dp[i]=max(dp[i],dp[j]+mm*(sum[i]-sum[j]));
                ++bkt[p][a[j]];
            }
            fordown(j,R[blg[i-m]],i-m){
                --bkt[p][a[j]];
            }
        }
        if(i==R[blg[i]]){
            work(L[blg[i]],R[blg[i]],0,n,blg[i]);
            getconv(blg[i]);
            // forup(j,0,n){
            //     msg("%lld ",mxv[blg[i]][j]);
            // }
            // msg("|\n");
        }
            // msg("%lld ",dp[i]);
    }
    // msg("|\n");
    printf("%lld\n",dp[n]);
}
/*
10 4
1 2 0 9 3 10 7 0 9 8 

*/