#include <bits/stdc++.h>
#define ll long long
#define ii pair<ll,ll>
#define fi first
#define se second
using namespace std;
const int N=1e5+6;
int n,k;
vector<ii>v;
vector<ii>v1(N);
int a1[N];
ll tong=0;
int main()
{
cin >>n >>k;
for(int i=1;i<=n;i++){
ll x;
cin >>x;
ll y=x+1;
v1[i]={x,y};
}
for(int i=2;i<=n;i++){
ll s=v1[i].fi-v1[i-1].se;
v.push_back({s,i});
}
sort(v.begin(),v.end(),greater<ii>());
for(int i=0;i<k-1;i++){
a1[v[i].se]=1;
}
ll sum=v1[1].fi;
for(int i=1;i<=n;i++){
if(a1[i+1]==1){
ll s1=v1[i].se-sum;
sum=v1[i+1].fi;
tong+=s1;
}
}
tong+=(v1[n].se-sum);
cout << tong;
return 0;
}
/*
3 3
1
3
6
*/
