#include <bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define ll long long
#define all(v) v.begin(), v.end()
#define fr(n) for(ll i=0;i<n;++i)
#define ctz(x) __builtin_ctzll(x)
#define clz(x) __builtin_clzll(x)
#define pcount(x) __builtin_popcountll(x)
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};
// #define cin fin
// #define cout fout
// ifstream fin
// ofstream fout
//const ll maxn = 3e5 + 5;
//int f[maxn],nf[maxn],inv[maxn];
//const int M=998244353;
//void init(){
//inv[1]=1; for (int i=2;i<maxn;i++) inv[i]=M-1ll*(M/i)*inv[M%i]%M;
//f[0]=nf[0]=1; for (int i=1;i<maxn;i++) f[i]=1ll*f[i-1]*i%M,nf[i]=1ll*nf[i-1]*inv[i]%M;
//}
//int C(int x,int y){return 1ll*f[x]*nf[y]%M*nf[x-y]%M;}
void solve(){
ll n, k;cin>>n>>k;
vector<ll> v;
fr(n){
ll x;cin>>x;v.push_back(x);
}
vector<ll> a;
for(ll i=1; i<n; i++){
a.push_back(v[i]-v[i-1]-1);
}
sort(all(a));
ll ans=n;
for(ll i=0; i<n-k; i++){
ans+=a[i];
}
cout<<ans;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(NULL);
// ll t;cin>>t;while(t--){solve();cout<<endl;}
solve();
}
