// teddybear's code
// the one who loves NBP
// noe the second
// goal: 0 / 8
// get medal in APIO (like TKN)
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
// prob:
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#define FOR(i,n) for (int i = 0; i<n; i++)
using ll = long long;
using ull = unsigned long long;
ll n,m,t;
ll cnt = 0;
const int maxn = 1e5;
const ll mod = 1e9 + 7;
#define Y "YES"
#define N "NO"
ll a[2 * maxn + 5];
bool visited[1005][1005];
int dist[1005][1005];
int w,h;
int fx[4] = {-1, 1, 0, 0};
int fy[4] = {0, 0, -1, 1};
queue <pair<int,int>> q;
ll dis[2 * maxn + 5];
void solve()
{
cin >> n >> m;
for (int i = 1; i<=n; i++)
{
cin >> a[i];
}
/*if (n == m)
{
cout << n;
return;
}*/
ll total_time = a[n] - a[1] + 1;
for (int i = 1; i<=n-1; i++)
{
dis[i] = a[i+1] - a[i] - 1;
}
sort(dis+1,dis+n, greater<ll>());
for (int i = 1; i<m; i++)
{
total_time -= dis[i];
}
cout << total_time;
}
void init()
{
int te = 1; //cin >> te;
while (te--)
{
solve();
}
}
void preprocess()
{
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//cin.tie(0); cout.tie(0);
//freopen(".inp", "r", stdin);
//freopen(".out", "w", stdout);
init();
preprocess();
//solve();
return 0;
}
