#include <bits/stdc++.h>
#define FOR(i,s,e) for(int i=(s);i<(int)(e);i++)
#define FOE(i,s,e) for(int i=(s);i<=(int)(e);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(x) (x).begin(), (x).end()
#define CLR(s) memset(s,0,sizeof(s))
#define PB push_back
#define x first
#define y second
using namespace std;
typedef long long LL;
typedef pair<int,int> pii;
typedef pair<LL, LL> pll;
typedef map<int,int> mii;
typedef vector<int> vi;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int N, K; cin >> N >> K;
int X, Y; cin >> X;
vi A;
REP(_, N - 1) {
cin >> Y;
if (Y - X - 1 != 0) {
A.PB(Y - X - 1);
}
X = Y;
}
sort(ALL(A));
LL Ans = N;
REP(i, max(0, int(A.size()) - K + 1)) Ans += A[i];
cout << Ans << endl;
return 0;
}
