#include<fstream>
#include<cstdio>
#include<set>
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#include<cstring>
#include<bitset>
#include<cmath>
#include<iomanip>
#include<queue>
#define f cin
#define g cout
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ll long long
#define bit 20
#define inf 500000000
#define base 256
#define ba 255
#define N 5000100
#define mod  1999999973
#define inu "deque.in"
#define outu "deque.out"
using namespace std;
ifstream f(inu);
ofstream g(outu);
//int dx[]={0,0,0,1,-1};
//int dy[]={0,1,-1,0,0};
ll S;
deque<int> D;
int n,k,A[N];
int main ()
{
    f>>n>>k;
    FOR(i,1,n)
    {
        f>>A[i];
        while(!D.empty()&&A[D.back()]>=A[i]) D.pop_back();
        D.push_back(i);
        if(D.front()<=i-k)
        D.pop_front();
        if(i>=k)
        S+=A[D.front()];
    }
    g<<S;
    return 0;
}