#include<cstdio>
#include<string>
#include<deque>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "deque";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

typedef long long int lld;
const int NMAX = 5000000 + 5;

int N, K;
int A[NMAX];
deque<int> D;
lld sol;

int main() {
    int i;

    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);

    scanf("%d%d", &N, &K);

    for(i = 1; i <= N; i++) {
        scanf("%d", &A[i]);

        while(!D.empty() && i - D.front() + 1 > K)
            D.pop_front();

        while(!D.empty() && A[D.back()] >= A[i])
            D.pop_back();

        D.push_back(i);

        if(i >= K)
            sol += 1LL * A[D.front()];
    }

    printf("%lld\n", sol);

    return 0;
}