#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = atcoder::static_modint<998244353>;
// using mint = atcoder::static_modint<1000000007>;
using ld = long double;
using ll = long long;
#define mp(a,b) make_pair(a,b)
#define rep(i,s,n) for(int i=s; i<(int)n; i++)
const vector<int> dx{1,0,-1,0},dy{0,1,0,-1};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n,k;cin >> n >> k;
    vector<ll> a(n);rep(i,0,n)cin >> a[i];
    while(a.size()>k && a.back()<=0)a.pop_back();
    n=a.size();

    priority_queue<ll> Q;
    ll s=0;
    Q.push(0);
    for(int i=n-1; i>=1; i--){
        s+=a[i];
        Q.push(s);
    }
    ll ans=accumulate(a.begin(),a.end(),0LL);
    rep(i,0,k-1)ans+=Q.top(),Q.pop();
    cout<< ans;
}