#pragma region
#include<bits/stdc++.h>
#define int long long
#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector,fast-math")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma comment(linker, "/stack:200000000")
#define f2(i, m) for(int i=0; i<m; i++)
#define f21(i, m) for(int i=1; i<m; i++)
#define f3(i, n, m) for(int i=n; i<m; i++)
#define f2_(i, m) for(int i=m; i>-1; i--)
#define f21_(i, m) for(int i=m; i>0; i--)
#define f3_(i, n, m) for(int i=n; i>=m; i--)
#define travG(idx) for(int i : g[idx])
#define travG_(i, idx) for(int i : g[idx])
#define trav(loop) for(int i : loop)
#define trav_(i, loop) for(int i : loop)
#define trav2(loop, idx) for(int i : loop[idx])
#define trav2_(i, loop, idx) for(int i : loop[idx])
#define ll long long
#define bs bitset
#define pii pair<int, int>
#define vi vector<int>
#define vvi vector<vector<int>>
#define ve vector<element>
#define ve_ vector<element_>
#define vpii vector<pair<int, int>>
#define dqi deque<int>
#define dqpii deque<pii>
#define qi queue<int>
#define qe queue<element>
#define qpii queue<pair<int, int>>
#define si stack<int>
#define se stack<element>
#define spii stack<pair<int, int>>
#define vb vector<bool>
#define pqi priority_queue<int>
#define pqi_ priority_queue<int, vi, greater<int>>
#define pqpii priority_queue<pair<int, int>>
#define pqpii_ priority_queue<pair<int, int>, vpii, greater<pii>>
#define pb push_back
#define pf push_front
#define pob pop_back()
#define pof pop_front()
#define len length()
#define elif else if
#define mod 1000000007
#pragma endregion
#define debug
/*
#ifdef debug
#endif
#ifndef debug
#endif
*/
using namespace std;
constexpr int mxn = 2e5+1;
signed main()// https://pintia.cn/problem-sets/91827364500/exam/problems/type/7?problemSetProblemId=91827368730&page=24
{ ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, k; cin>>n>>k;
k = n-k;
int ans = n;
int t1, t2; cin>>t1;
priority_queue<int, vi, greater<int>> pq;
f2(i, n-1)
{
cin>>t2;
pq.push(t2-t1-1);
t1 = t2;
}
f2(i, k)
{
ans += pq.top();
pq.pop();
}
cout << ans;
return 0;
}
