#include <bits/stdc++.h>
#define fi first
#define se second
#define lc id<<1
#define rc id<<1^1
#define nmax 100008
using namespace std;
typedef pair<int, int> pii;
int n, k, ans, a[nmax];
vector<int>vt;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
// freopen("file.inp", "r", stdin);
// freopen("file.out", "w", stdout);
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> a[i];
ans = a[n] - a[1] + 1;
for (int i = 2; i <= n; i++)
vt.push_back(a[i] - a[i - 1] - 1);
sort(vt.begin(), vt.end());
while (--k){
ans -= vt.back();
vt.pop_back();
}
cout << ans;
return 0;
}
