#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#define tof_io ios_base::sync_with_stdio(false);cin.tie(0) , cout.tie(0);
#define double long double
#define int long long
#define pb push_back
#define all(x) x.begin(),x.end()
#define endl '\n'
const int mod = 998244353; //998244353 1e9+7 1e9+9
const int inf = 1e18;
const int N = 1e6 + 23;
const int lg = 23;
int fac[N];
int inv[N];
int dnt_pow (int a, int b, int md = mod){int ans = 1; while(b){if(b&1){ans = (a*ans)%md;}a = (a*a)%md;b >>= 1;}return ans ;}
void dnt_bld (){fac[0] = 1; inv[0] = dnt_pow(fac[0],mod-2) ;for(int i = 1 ; i < N ; i++) {fac[i] = (fac[i-1] * i) % mod;inv[i] = dnt_pow( fac[i] , mod-2);}}
int dnt_ncr (int r,int n){if(r>n) return 0; return fac[n] * inv[r] % mod * inv[n-r] % mod;}
int32_t main()
{
int n, k;
cin >> n >> k;
k--;
int sm = 1;
priority_queue<int> pq;
int y = 0;
for(int i = 0; i < n; i++)
{
int x;
cin >> x;
if(i!=0)
{
sm = sm + x - y;
pq.push(x-y-1);
}
y = x;
}
for ( int i = 0; i < min(k,n) ; i++)
{
sm = sm - pq.top();
pq.pop();
}
cout << sm ;
}
