import std.stdio, std.string, std.conv, std.algorithm, std.numeric;
import std.range, std.array, std.math, std.typecons, std.container, core.bitop;


void main() {
    int n, k;
    scan(n, k);

    auto a = readln.split.to!(long[]);
    a.sort();

    auto d = new long[](n-1);
    foreach (i ; 0 .. n - 1) {
        d[i] = a[i+1] - a[i];
    }

    d.sort();

    long ans;

    foreach (i ; 0 .. n - k) {
        ans += d[i];
    }

    writeln(ans);
}



void scan(T...)(ref T args) {
    string[] line = readln.split;
    foreach (ref arg; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}



void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}