/*#pragma GCC optimize("O3")
#pragma GCC optimization("Ofast,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")*/
#include <bits/stdc++.h>
/*#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>*/
#define ll int
#define ll1 long long
#define ull unsigned long long
#define dou long double
#define str string
#define vll vector<ll>
#define vi vector<int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vbool vector<bool>
#define vstr vector<str>
#define vvll vector<vll>
#define pb push_back
#define pf push_front
#define endl "\n"
#define fr first
#define se second
// #define sortcmp(a) sort(a.begin(), a.end(), cmp)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define INF 1000000007
#define ordered_set tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>
using namespace std;
//using namespace __gnu_pbds;
mt19937 rng(time(0));
ll randll(ll l, ll r) {
return uniform_int_distribution<ll>(l, r)(rng);
}
int main(){
speed;
srand(time(0));
ll n, k;
cin >> n >> k;
vll a(n);
for (int i = 0; i < n; i ++) {
cin >> a[i];
}
ll res = a[n-1]+1-a[0];
vll b;
for (int i = 0; i < n-1; i ++) {
b.pb(a[i+1]-a[i]-1);
}
sort(b);
reverse(b);
for (int i = 0; i < k-1; i ++) {
res -= b[i];
}
cout << res << endl;
}
