#include<bits/stdc++.h>
#define STIZE(x) fprintf(stderr, "STIZE%d\n", x);
#define PRINT(x) fprintf(stderr, "%s = %d\n", #x, x);
#define NL(x) printf("%c", " \n"[(x)]);
#define lld long long
#define pii pair<int,int>
#define pb push_back
#define fi first
#define se second
#define mid (l+r)/2
#define endl '\n'
#define all(a) begin(a),end(a)
#define sz(a) int((a).size())
#define LINF 1000000000000000LL
#define INF 1000000000
#define EPS 1e-9
using namespace std;
#define MAXN 100010
int N, K, a[MAXN], rez;
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); cerr.tie(0);
cin >> N >> K;
for(int i = 1; i <= N; i++) cin >> a[i];
sort(a+1, a+1+N);
rez = a[N]-a[1]+1;
for(int i = N; i >= 2; i--) a[i] = a[i]-a[i-1]-1;
sort(a+2, a+1+N);
for(int i = 0; i < K-1; i++) rez -= a[N-i];
cout << rez;
}
