#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    int N,M;
    cin >> N >> M;
    vector<ll> V(N),dif(N-1);
    rep(i,0,N)cin >> V[i];
    sort(V.begin(), V.end());
    ll sum = V.back() - V.front();
    rep(i,0,N-1)dif[i] = V[i+1] - V[i];
    sort(dif.rbegin(), dif.rend());
    rep(i,0,M-1)sum -= dif[i];
    cout << sum << endl;
}