#include <bits/stdc++.h>
using namespace std;
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroint-loops")
#pragma GCC optimization("Ofast")
#define all(v) v.begin(), v.end()
const int mxN = 1e9+100;
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n,k;cin>>n>>k;
int ar[n+1];
for(int i=1;i<=n;++i) cin>>ar[i];
vector<int> vec;
for(int i=2;i<=n;++i){
vec.emplace_back(ar[i-1]-ar[i]+1);
}
sort(all(vec));
//4,4 totalOn-totalOf
int ans=ar[n]-ar[1]+1;
int lim=min(k-1,(int)vec.size());
for(int i=0;i<lim;++i){
ans+=vec[i];
}
cout<<ans;
return 0;
}
