#include <bits/stdc++.h>
using namespace std;
#define ll                 long long 
#define all(v)             v.begin(), v.end()
ll ceil2(ll a, ll b) {
return (a + b - 1) / b;
}
// #include <ext/pb_ds/assoc_container.hpp> 
// #include <ext/pb_ds/tree_policy.hpp> 
// using namespace __gnu_pbds; 
// #define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 



void solve(){
    ll n, m;cin>>n>>m;
    // vector<ll> v;
    // for(int i=0 ;i<n; i++){
    //     ll x;cin>>x;v.push_back(x);
    // }
    multiset<ll > s;
    queue<ll> q;
    for(int i=0; i<m; i++){
        ll x;cin>>x;
        s.insert(x);
        q.push(x);
    }
    ll sum=*s.begin();
    for(int i=m; i<n; i++){
        ll x;cin>>x;
        s.erase(q.front());
        q.pop();
        q.push(x);
        s.insert(x);
        sum+=*s.begin();
    }
    cout<<sum;
}


int main(){
    freopen("deque.in", "rt", stdin);
	freopen("deque.out", "wt", stdout);
   ios_base::sync_with_stdio(false); cin.tie(NULL);
//    ll t;cin>>t;while(t--){solve();cout<<endl;}
    solve();
}