#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
mt19937_64 rng((int)std::chrono::steady_clock::now().time_since_epoch().count());
const int MAXN = 3e5 + 10;
const int MOD = 1e9 + 7;
#define int long long
int rnd(int x, int y) { // random number generator
int u= uniform_int_distribution<int>(x, y)(rng); return u;
}
void solve(int tc) {
int N, K;
cin >> N >> K;
if(N == 1) {
cout << "1\n"; return;
}
int t[N];
for(int i=0; i<N; i++) {
cin >> t[i];
}
priority_queue<int> s;
for(int i=1; i<N; i++) s.push(t[i]-1 - t[i-1]);
int ans = t[N-1] + 1 - t[0];
while(K > 1) {
K--;
ans -= s.top();
s.pop();
}
cout << ans << "\n";
}
int32_t main(){
ios::sync_with_stdio(0); cin.tie(0);
int t = 1; //cin >> t;
for(int i=1; i<=t; i++) solve(i);
}
