#include<bits/stdc++.h>
#define int long long
#define pb push_back
#define ALL(x) x.begin(),x.end()
#define fi first
#define se second
#define ist insert
using namespace std;
typedef long long ll;
const int N=200005;
const int MOD=1000000007;//998244353
const int INF=2147483647;//1700000000000000000
int n,k;
int a[N];
int b[N];
inline void sol(){
cin >>n>>k;
for (int i=1;i<=n;i++)
cin >>a[i];
for (int i=1;i<n;i++)
b[i]=a[i+1]-a[i];
sort(b+1,b+n);
int ans=n;
for (int i=1;i<=n-k;i++)
ans+=b[i]-1;
cout <<ans<<'\n';
}
signed main(){
int _=1;
//cin >>_;
while (_--) sol();
return 0;
}
