#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define pb push_back
#define mk make_pair
#define F first
#define S second
using namespace std;
const int L=1e7+11;
const ll N=2e4+10;
const ll mod=1e9+7;
const ll inf=3e18;
const double pi=3.14159265359;
ll lcm(ll a, ll b){ return (a/__gcd(a,b))*b; }
void solve(){
int n,k;
cin>>n>>k;
int a[n+1];
for(int i=1; i<=n; i++){
cin>>a[i];
}
if(k>=n){
cout<<n<<endl;
return;
}vector<int>b;
int ans=k,d=n-k,i=0;
for(int i=2; i<=n; i++){
b.pb(a[i]-a[i-1]);
}sort(b.begin(), b.end());
while(i<d){
ans+=b[i];
i++;
}
cout<<ans<<endl;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", " w", stdout);
int tt=1;
// cin>>tt;
while(tt--){
solve();
}
}
