#include <iostream>
#include <stdio.h>
#include <vector>
#include <algorithm>
#define int long long
const int MAX = 1e5 + 15;
int aGuest;
int aMatch;
std::vector<int> Time;
std::vector<int> diff;
signed main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(NULL);
std::cout.tie(NULL);
std::cin >> aGuest >> aMatch;
for (int i = 0; i < aGuest; ++i) {
int inp;
std::cin >> inp;
Time.push_back(inp);
}
for (int i = 1; i < aGuest; ++i) {
diff.push_back(Time[i] - Time[i - 1]);
}
std::sort(diff.begin(), diff.end());
int ans = 0;
for (int i = 0; i < aGuest - aMatch; ++i) {
ans += diff[i];
}
std::cout << ans + aMatch;
}
