#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#ifdef lisie_bimbi
#else
#define endl '\n'
#endif
typedef long long ll;
const ll inf = 1'000'000'000'000'000'000;
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC target("avx,avx2,bmi2,fma,popcnt")
//#define int long long
void solve(){
int n, k;
cin >> n >> k;
vector<int> t(n);
for(int i = 0; i < n; i++){
cin >> t[i];
}
k--;
vector<int> z(n - 1);
for(int i = 0; i < n - 1; i++){
z[i] = t[i + 1] - t[i] - 1;
}
std::sort(z.rbegin(), z.rend());
int ans = t.back() + 1 - t[0];
for(int i = 0; i < k; i++){
ans -= z[i];
}
cout << ans << endl;
}
signed main(){
#ifdef lisie_bimbi
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#else
cin.tie(nullptr)->sync_with_stdio(false);
#endif
cout << setprecision(5) << fixed;
int _ = 1;
//cin >> t;
while(_--){
solve();
}
return 0;
}
