#include <bits/stdc++.h>
#include <queue>
#define pb push_back
#define F first
#define S second
#define rep(X, a,b) for(int X=a;X<b;++X)
#define ALL(a) (a).begin(), (a).end()
#define SZ(a) (int)(a).size()
#define NL "\n"
using namespace std;
typedef pair<long long,long long> pll;
typedef pair<int,int> pii;
typedef long long ll;
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << "," << p.second << ')'; }
template<typename A> ostream& operator<<(ostream &os, const vector<A> &p){
for(const auto &a:p)
os << a << " ";
os << "\n";
return os;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n, k;
cin>>n>>k;
vector<ll> te(n);
rep(i,0,n) cin>>te[i];
ll ans=n;
priority_queue<ll, vector<ll>, greater<ll>> pq;
rep(i,1,n){
pq.push(te[i]-te[i-1]);
}
while(n>k){
ans+=pq.top()-1;
pq.pop();
n--;
}
cout<<ans<<NL;
}
