#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; i++)
#define FORD(i, b, a) for (int i = (b), _a = (a); i >= _a; i--)
#define BIT(mask,i) ((mask >> i) & 1ll )
#define endl '\n'
#define all(x) x.begin(),x.end()
#define ii pair <int,int>
using namespace std;
template<class X, class Y>
bool minimize(X &x, const Y &y) {
if (x > y) {
x = y;
return true;
} else return false;
}
template<class X, class Y>
bool maximize(X &x, const Y &y) {
if (x < y) {
x = y;
return true;
} else return false;
}
template<class T>
T Abs(const T &x) {
return (x < 0 ? -x : x);
}
const long long oo = 1e18;
const int N = 1e6+5;
const int MOD = 1e9+7;
int a[N];
int n,k;
int check(int x)
{
int cnt = 0;
FOR(i,1,n-1)
{
if (a[i+1] - a[i] > x)
cnt++;
}
return cnt;
}
void PhongCach()
{
cin >> n >> k;
FOR(i,1,n) cin >> a[i];
vector <int> V;
FOR(i,1,n-1) V.push_back(-a[i+1] + a[i]);
sort(all(V));
int ans = a[n] - a[1] + k;
FOR(i,0,k-2) ans+= V[i];
cout << ans;
return;
}
#define TASK "task"
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen(TASK".inp","r",stdin);
//freopen(TASK".out","w",stdout);
int Sty1e = 1;
// cin >> Sty1e;
while (Sty1e--) PhongCach();
return 0;
}
