1 #include<algorithm>
 2 #include<iostream>
 3 #include<iomanip>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<cstdio>
 7 #include<vector>
 8 #include<cmath>
 9 #include<queue>
10 #include<stack>
11 #include<map>
12 #include<set>
13 #define ll long long
14 #define rep(i,a,b) for(register int i=a;i<=b;++i)
15 #define re register
16 using namespace std;
17 const int N=100010;
18 ll dp[2][N],C[N];
19 int n,q[N];
20 inline ll gi( )
21 {
22     ll ret=0;char ch=getchar();
23     while(ch<‘0‘||ch>‘9‘) ch=getchar();
24     while(ch>=‘0‘&&ch<=‘9‘) ret=ret*10+ch-‘0‘,ch=getchar();
25     return ret;
26 }
27 ll getnum(int now,int i,int bj) {
28     return dp[!bj][i] + C[i]*(C[now]-C[i]);
29 }
30 bool cale(int l1,int l2,int l3,int bj) {
31     ll b1= dp[!bj][l1]-C[l1]*C[l1],b2=dp[!bj][l2] - C[l2]*C[l2] , b3=dp[!bj][l3] - C[l3]*C[l3];// bug
32     return (b3-b2)*(C[l1]-C[l2]) <= (b2-b1)*(C[l2]-C[l3]);
33 }
34 int main( )
35 {
36 
37     n=gi();int k=gi();
38     rep(i,1,n) C[i]=gi(),C[i]+=C[i-1];
39     re int bj=1,hd,tl;
40     for(re int u=1;u<=k;u++) {
41         bj=!bj;
42         hd=tl=0;q[0]=0;
43         for(re int i=1;i<=n;i++) {
44             while(hd+2<=tl&&cale(q[tl-2],q[tl-1],q[tl],bj)) q[tl-1]=q[tl--];//
45             while(hd<tl&&getnum(i,q[hd],bj)<=getnum(i,q[hd+1],bj)) hd++;
46             dp[bj][i]=getnum(i,q[hd],bj);
47             q[++tl]=i;
48         }
49     }
50     printf("%lld",dp[bj][n]);
51     return 0;
52 }