#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef pair<ii, int> ri3;
#define mp make_pair
#define pb push_back
#define fi first
#define sc second
#define SZ(x) (int)(x).size()
#define ALL(x) begin(x), end(x)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define FOR(i, a, b) for (int i = a; i <= b; ++i)
#define RFOR(i, a, b) for (int i = a; i >= b; --i)
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false);
cin.tie(0);
int n, k; cin >> n >> k;
int t[n];
FOR(i,0,n-1){
cin >> t[i];
}
int diff[n-1];
FOR(i,1,n-1){
diff[i-1] = t[i]-1-t[i-1];
}
sort(diff, diff+n-1, greater<int>());
int ans = t[n-1]-t[0]+1;
FOR(i,0,k-2){
ans -= diff[i];
}
cout << ans << '\n';
}
