#include<bits/stdc++.h>
#define endl "\n"
using namespace std ;
typedef long long ll;
typedef long double ld ;
#define pb push_back
#define pp pop_back
const int N=1e6+9;
const ll inf=1e18 ;
const ll mod = 1e9+9 ;
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
ll n ,a[N] , x, y,k,t[N];
vector<ll>vec;
void solve(){
cin>>n>>k;
for(int i=0;i<n;i++) cin>>t[i];
for(int i=0;i<(n-1);i++)vec.pb(t[i+1]-t[i]-1);
sort(vec.begin(),vec.end());
ll ans=0;
for(int i=0;i<(n-k);i++){
ans+=vec[i];
}
cout<<n+ans;
}
int main(){
fast;
ll t=1;//cin>>t;
while(t--)solve();
return 0;
}
