#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
const int INF = 2147483645;
const int maxN = (int)2e5+5;
const ll LLINF = LLONG_MAX;
const ll mod = 998244353;
//const ll mod = 1000000007;
void solv() {
ll n, k, a;
vector<ll> v, diff;
cin>>n>>k;
for (int i=0;i<n;i++){
cin>>a; v.pb(a);
}
for (int i=0;i<n-1;i++) {
ll res = v[i+1]-v[i];
diff.pb(res);
}
sort(diff.begin(), diff.end());
ll ans = n;
for (int i=0;i<n-k;i++) {
ans -= 1;
ans += diff[i];
}
cout<<ans<<'\n';
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int t=1;
// cin>>t;
while (t--) solv();
}
