#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
using namespace std;
// using namespace __gnu_pbds;
#define file(name) freopen(name".inp", "r", stdin);\
freopen(name".out", "w", stdout);
#define ordered_set tree<ll, null_type,less_equal<ll>, rb_tree_tag,tree_order_statistics_node_update>
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define all(a) a.begin(),a.end()
#define endl "\n"
#define all1(a) a+1,a+n+1
#define unordered_map map
#define Accepted 0
// #define push_back emplace_back
// #define gcd(a,b) __gcd(a,b);
// #define lcm(a,b) (a*b)/gcd(a,b);
const long long INF = (long long)1e9;
const long long MOD = (long long)1e9+7;
const long long MODD = 14062008; /// 998244353
const long long maxN = 2e5+9;
const long long LOG = 30;
///--------------------------------
void solve();
int main(){
long long t;
// cin >> t;
t=1;
while (t--){
solve();
}
return Accepted;
}
///--------------------[PROBLEM SOLUTION]--------------------///
int n,k,ans=INF,a[200009],truoc=0;
vector<pair<int,int>> luu;
priority_queue<int> luu1;
void solve(){
cin >> n >> k;
int x;
cin >> x;
ans=x;
truoc=x;
for (int i=1; i<=n-1; i++){
cin >> x;
luu.push_back({x,x+1});
luu1.push(x-truoc-1);
truoc=x;
}
if(n==1) return cout << 1, void();
ans=x-ans+1;
k--;
while (k--){
ans-=luu1.top();
luu1.pop();
}
cout << ans;
}
