var g = [], n = 0, k = 0, a = [];

function f(m) {
    
    if (m >= n) return 0;
    if (g[m] != -1) return g[m];
    var min = 0; 
    for (var i=0;i<=k;i++) if (m+i<n) {
        var r = a[m+i]+f(m+i+k+1);
        if (r < min || i==0) min = r;
    }
    g[m] = min;
    return g[m];
}

function processData(input) {
    var a1 = input.split("\n");
    var a2 = a1[0].split(" ").map(Number);
    n = a2[0];
    k = a2[1];
    a = a1[1].split(" ").map(Number);
    for (var i=0;i<n;i++) {
        g[i] = -1;        
    }
    console.log(f(0));    
} 

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

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