#include <bits/stdc++.h>
#define coutf(n, m) cout << fixed << setprecision(n) << m
#define forr(i, a, n) for (int i = a; i < n; i++)
#define forl(i, a, n) for (int i = a; i > n; i--)
#define macos ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endll "\n"
#define sp " "
typedef long long ll;
using namespace std;
const int N = 1e5 + 10;
int n,k,ans;
int a[N],dp[N];
vector<int> A;
int main(){macos;
cin >> n >> k;
forr(i,1,n+1)cin >> a[i];
forr(i,2,n+1)A.push_back(a[i]-a[i-1]);
ans = a[n] - a[1] + 1;
sort(A.begin(),A.end());
forr(i,0,n-k)ans -= A[i];
cout << ans;
return 0;
}
