#include <bits/stdc++.h>
#define int int64_t
#define pb push_back
#define vecint vector <int>
#define double long double
const int mod = 1e9 + 7;
const int N = 2e5 + 7;
const long long inf = 1e18;
const int NN = 107;
using namespace std;
/*vecint t(N * 4), a(N);
void build(int v, int tl, int tr) {
if (tl == tr) {
t[v] = a[tl];
return;
}
int tm = (tl + tr) / 2;
build(v * 2, tl, tm);
build(v * 2 + 1, tm + 1, tr);
t[v] = min(t[v * 2], t[v * 2 + 1]);
}
void update(int v, int tl, int tr, int pos, int x) {
if (pos > tr || pos < tl) {
return;
}
if (tl == tr) {
t[v] = x;
return;
}
int tm = (tl + tr) / 2;
update(v * 2, tl, tm, pos, x);
update(v * 2 + 1, tm + 1, tr, pos, x);
t[v] = min(t[v * 2], t[v * 2 + 1]);
}
int get(int v, int tl, int tr, int l, int r) {
if (l > tr || r < tl) {
return inf;
}
if (l <= tl && tr <= r) {
return t[v];
}
int tm = (tl + tr) / 2;
return min(get(v * 2, tl, tm, l, r), get(v * 2 + 1, tm + 1, tr, l, r));
}*/
void solve() {
int n, k;
cin >> n >> k;
k--;
vecint a(n + 1);
for(int i = 1; i <= n; i++) {
cin >> a[i];
}
int ans = a[n] - a[1] + 1;
vecint b(n);
for(int i = 1; i < n; i++) {
b[i] = a[i + 1] - a[i] - 1;
}
sort(b.begin() + 1, b.end());
reverse(b.begin() + 1, b.end());
for(int i = 1; i <= k; i++) {
ans -= b[i];
}
cout << ans;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int tt = 1;
//cin >> tt;
while (tt--){
solve();
}
}
