1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=10000005,inf=1e9;
 4 int head[N],d[N],f[N],l[N],r[N],a[N],s=1e9,t,n,k,cnt=-1,cost;
 5 bool v[N];
 6 struct node{
 7     int to,nex,f,w,c;
 8 }e[1000005];
 9 void add(int x,int y,int w,int c)
10 {
11     e[++cnt].to=y;e[cnt].w=w;e[cnt].f=x;e[cnt].c=c;e[cnt].nex=head[x];head[x]=cnt;
12     e[++cnt].to=x;e[cnt].w=0;e[cnt].f=y;e[cnt].c=-c;e[cnt].nex=head[y];head[y]=cnt;
13 }
14 queue<int>q;
15 bool spfa()
16 {
17     memset(f,-1,sizeof(f));
18     memset(d,0x3f,sizeof(d));
19     memset(v,0,sizeof(v));
20     d[s]=0;v[s]=1;q.push(s);
21     while(!q.empty())
22     {
23         int x=q.front();q.pop();v[x]=0;
24         for(int i=head[x];i!=-1;i=e[i].nex)
25         {
26             int y=e[i].to;
27             if(d[y]<=d[x]+e[i].c||!e[i].w)continue;
28             d[y]=d[x]+e[i].c;f[y]=i;
29             if(!v[y])q.push(y),v[y]=1;
30         }
31     }
32     if(d[t]>1e9)return 0;
33     int flow=inf;
34     for(int i=f[t];i!=-1;i=f[e[i].f])
35     flow=min(flow,e[i].w);
36     for(int i=f[t];i!=-1;i=f[e[i].f])
37     e[i].w-=flow,e[i^1].w+=flow,cost+=e[i].c*flow;
38     return 1;
39 }
40 int main()
41 {
42     scanf("%d%d",&n,&k);int num=0;
43     memset(head,-1,sizeof(head));
44     for(int i=1;i<=n;++i)
45     {
46         scanf("%d%d",&l[i],&r[i]);
47         a[++num]=l[i];a[++num]=r[i];
48     }
49     sort(a+1,a+1+num);
50     num=unique(a+1,a+1+num)-a-1;
51     for(int i=1;i<=n;++i)
52     {
53         int x=r[i]-l[i];
54         l[i]=lower_bound(a+1,a+1+num,l[i])-a;
55         r[i]=lower_bound(a+1,a+1+num,r[i])-a;
56         add(l[i],r[i],1,-x);
57     }
58     for(int i=1;i<num;++i)
59     add(i,i+1,k,0);t=num+1;
60     add(num,t,k,0);
61     add(0,1,k,0);s=0;
62     while(spfa());
63     printf("%d\n",-cost);
64     return 0;
65 }