#include <bits/stdc++.h>
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//#pragma GCC optimize("Ofast")
//1.0 * clock() / CLOCKS_PER_SEC
#define fi first
#define se second
#define ll long long
#define dl double long
using namespace std;
const ll NN = 1e10 + 7;
const int N = 1e6 + 7;
const int M = 6;
const ll mod = 1e9 + 7;
const ll inf = 1e18 + 7;
const dl rf = 1e-14;
const int B = sqrt(N);
int n,k;
int a[N];
void solve1()
{
cin >> n >> k;
for( int i = 1; i <= n; i++ ){
cin >> a[i];
}
vector < int > v;
for( int i = 1; i < n; i++ ){
v.push_back(a[i + 1] - a[i] - 1);
}
sort( v.begin() , v.end() );
int ans = 0;
for( int i = 0; i < (int)v.size() - k + 1; i++ ){
ans += v[i];
}
cout << ans + n;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
//freopen( "input.txt" , "r" , stdin );
//freopen( "output.txt" , "w" , stdout );
int cghf = 1;//cin >> cghf;
while( cghf-- ){
solve1();
}
}
