'use strict';

let debug = true;

function processData(input) {
    let lines = input.split("\n");
    let cols = lines[0].split(" ");
    let n = parseInt(cols[0]) || 0;
    let k = parseInt(cols[1]) || 0;
    //Enter your code here
    
    let costs = lines[1].split(" ");
    let list = [];
    let costMap = {};
    
    let minCost = -1;
    let maxCost = -1;
    for (let i = 0; i<costs.length; i++) {
        let cost = parseInt(costs[i]) || 0;
        if (minCost < 0 || cost < minCost) {
            minCost = cost;
        }
        if (maxCost < 0 || cost > maxCost) {
            maxCost = cost;
        }
    }
    
    if (debug) {
        console.error("min " + minCost);
        console.error("max " + maxCost)
    }
    for (let i = 0; i<costs.length; i++) {
        let cost = parseInt(costs[i]) || 0;
        let openPrio = maxCost - cost;
        
        let minIndex = Math.max(i-k, 0);
        let maxIndex = Math.min(i+k, list.length - 1);
        
        if (i != 0) {
            openPrio += maxCost;
        }
        if (i != costs.length - 1) {
            openPrio += maxCost;
        }
        
        for (let j = minIndex; j<=maxIndex; j++) {
            if (j === i) {
                continue;
            }
            openPrio += parseInt(costs[j]);
        }
        
        insert(list, costMap, i, openPrio);
    }
    
    if (debug) {
        console.error(list);
        console.error(costMap);
    }
    
    let visited = {};
    let totalCost = 0;
    for (let i =0 ; i<list.length; i++) {
        if (list[i] in visited) {
            continue;
        }
        let minIndex = Math.max(list[i]-k, 0);
        let maxIndex = Math.min(list[i]+k, list.length - 1);
        
        if (debug) console.error("close " + list[i]);
        totalCost += parseInt(costs[list[i]]) || 0;
        
        for (let j = minIndex; j<=maxIndex; j++) {
            if (j in visited) {
                continue;
            }
            visited[j] = 1;
            if (debug) console.error("visiting " + j);
        }
    }
    return totalCost;
}

function insert(list, costMap, index, cost) {
    let minPos = 0;
    let maxPos = list.length;
    while (minPos < maxPos - 1) {
        let dist = Math.floor((maxPos - minPos) / 2) || 1;
        if (cost < costMap[list[minPos]]) {
            minPos += dist;
        } else {
            maxPos -= dist;
        }
    }
    list.splice(minPos, 0, index)
    costMap[index] = cost;
    if (debug) {
        console.error("adding " + index +  " / " + cost + " on ", minPos);
        console.error(list);
    }
}



process.stdin.resume();
process.stdin.setEncoding("ascii");
let _input = "";
process.stdin.on("data", function (input) {
    _input += input;
});

process.stdin.on("end", function () {
   console.log(processData(_input));
});