#include <bits/stdc++.h>
using namespace std;
template<typename T>
void out(T x) { cout << x << endl; exit(0); }
#define watch(x) cout << (#x) << " is " << (x) << endl
using ll = long long;
const int maxn = 1e6 + 5;
int n, k;
int a[maxn];
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>>n>>k;
for (int i=0; i<n; i++) {
cin>>a[i];
}
sort(a,a+n);
priority_queue<int> gaps;
for (int i=0; i+1<n; i++) {
gaps.push(a[i+1]-a[i]-1);
}
int res = a[n-1]-a[0]+1;
for (int i=0; i<k-1; i++) {
res -= gaps.top();
gaps.pop();
}
cout<<res<<endl;
return 0;
}
