#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define pii pair<int,int>
#define pll pair<long long,long long>
#define pb push_back
#define debug(x) cerr<<#x<<"="<<x<<endl
#define pq priority_queue
#define inf 1ll<<60
#define rep(i,a,b) for (ll i=a;i<(b);i++)
#define MP make_pair
#define SZ(x) (int(x.size()))
#define mod 1000000007
#define ALL(x) x.begin(),x.end()
#define endl "\n"
void inc(ll &a,ll b) {a=(a+b)%mod;}
void dec(ll &a,ll b) {a=(a-b+mod)%mod;}
int prod(ll a,ll b) {return ll(a)*ll(b)%mod;}
int lowbit(ll x) {return x&(-x);}
ll p0w(ll base,ll p) {ll ret=1;while(p>0){if (p%2ll==1ll) ret=ret*base%mod;base=base*base%mod;p/=2ll;}return ret;}
const ll maxn=111111;
ll a[maxn],diff[maxn];
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
ll n,k;cin>>n>>k;
rep(i,1,n+1)cin>>a[i];
//spit into <=k intevals
//must contain the N points
//a[] is sorted
ll ans=n;
rep(i,2,n+1){
diff[i]=a[i]-(a[i-1]+1);
}
sort(diff+2,diff+n+1);
ll p=2;
while(n>k){
ans+=diff[p];
p++;
n--;
}
cout<<ans<<endl;
return 0;
}
