#include <bits/stdc++.h>
using namespace std;
const long long INFll = 1e18;
const int INFii = 1e9;
typedef long long ll;
typedef int ii;
typedef double dbl;
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define maxn 110000
//LEMBRAR DE MUDAR
ii n, k, ant, g[maxn];
int main() {
ios::sync_with_stdio(false); cin.tie(0);
//freopen("in.in", "r", stdin);
//freopen("____.out", "w", stdout);
cin >> n >> k;
cin >> ant;
ii ans = 1;
for(ii i = 1; i < n; i++) {
ii t;
cin >> t;
g[i] = t-ant-1;
ans+= g[i] + 1;
ant = t;
}
sort(g+1,g+1+n,greater<ii>());
k--;
for(ii i = 1; i <= k; i++) {
ans-= g[i];
}
cout << ans << endl;
return 0;
}
