#include <cstdio>
#include <cstdlib>
#include <cstddef>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <iostream>
#include <iomanip>
#define LL long long

int main(void)
{
    std::vector<LL> alist;
    int n, k;
    std::cin >> n >> k;
    for (int i = 0; i < n; i++) {
        LL a;
        std::cin >> a;
        alist.push_back(a);
    }
    std::sort(alist.begin(), alist.end());
    std::vector<LL> difflist;
    LL diffsum = 0;
    for (size_t i = 1; i < alist.size(); i++) {
        LL tmp = alist[i] - alist[i - 1];
        diffsum += tmp;
        difflist.push_back(tmp);
    }
    std::sort(difflist.begin(), difflist.end(), [](const LL& a, const LL& b) {return a > b; });
    for (int i = 0; i < k - 1; i++) {
        diffsum -= difflist[i];
    }
    std::cout << diffsum << std::endl;
    return 0;
}