#include <bits/stdc++.h>
#define respagold ios_base::sync_with_stdio(0), cin.tie(0);
#define int long long
#define ll long long
#define int2 __int128_t
#define FOR( i, x, n, d ) for( int i = x; i <= n; i += d )
#define FORR( i, x, n, d ) for( int i = x; i >= n; i -= d )
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x.size())
#define pb push_back
#define ins insert
#define lb lower_bound
#define ub upper_bound
#define pii pair <int, int>
#define ppi pair <pair <int, int>, int>
#define pip pair <int, pair <int, int>>
#define mkp make_pair
using namespace std;
const int N = 1e5 + 12;
const int mod = 1e9 + 7;
const int inf = 1e18;
int n, m, ans, a[N];
void solve()
{
cin >> n >> m;
multiset <int> st;
FOR( i, 1, n, 1 )
{
cin >> a[i];
if( i > 1 ) st.ins(-(a[i] - a[i - 1] - 1));
}
int ans = a[n] - a[1] + 1; m --;
while( m -- )
{
ans += *st.begin();
st.erase(st.begin());
}
cout << ans << '\n';
}
signed main()
{
respagold;
int test = 1;
if( !test ) cin >> test;
while( test -- ) solve();
}
