#include<bits/stdc++.h>
#define en "\n"
#define s second
#define f first
#define fast_io ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define vi vector<int>
#define vii vector<pair<int,int>>
#define int long long
#define rall(x) x.rbegin(), x.rend()
#define pb push_back
#define loop(a) for(int i = 0; i < a; i++)
#define loopv(i,a) for (int i = 0; i < a; i++)
#define all(x) (x).begin(), (x).end()
#define prDouble(x) printf("%.8f", x)
#define goog(tno) printf("Case #%d: ", tno)
using namespace std;
const int N = 300100;
void solve() {
int n, k;
cin>>n>>k;
int ans=0;
vi a(n);
for(int i=0; i<n; i++){
cin>>a[i];
}
vi b;
for(int i=1; i<n; i++){
b.pb(a[i]-a[i-1]-1);
}
sort(all(b));
for(int i=0; i<n-k; i++){
ans+=b[i];
// cout<<b[i]<<" ";
}
ans+=n;
cout<<ans<<en;
}
signed main() {
fast_io;
int tc = 1;
// scanf("%d", &tc);
while (tc--)
solve();
}
