#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 1e5 + 7;
int n, k, a[mxN], b[mxN];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
//freopen(task".INP", "r", stdin);
//freopen(task".OUT", "w", stdout);
cin >> n >> k;
a[0] = 0;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
b[i] = a[i] - a[i - 1];
}
sort(b + 2, b + n + 1, greater<int>());
int ans = a[n];
for (int i = 1; i <= k; i++)
ans = ans - b[i] + 1;
cout << ans;
}
