#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define fi first
#define sc second
const int mod = 1e+9;
int dp[1000000];
queue<int>q;
map<int,int>mp;
signed main(){
int n, k;
cin >> n >> k;
vector<int>a(n);
for(int i = 0; i < n; i++){
cin >>a[i];
}
if(n <= k)cout << n << endl;
else{
int bruh = 0;
vector<int>v;
for(int i = 0; i < n - 1; i++){
v.pb((a[i+1] - a[i]) - 1);
}
sort(v.rbegin(), v.rend());
for(int i = 0; i < k - 1; i++) {
bruh += v[i];
}
cout << (a[n-1] - a[0] + 1) - bruh << endl;
}
}
