def main():
    N, K = map(int, input().split())
    A = list(map(int, input().split()))
    sort_A = sorted(A)
    diff = [0] * (N - 1)
    for i in range(N-1):
        diff[i] = sort_A[i+1] - sort_A[i]
    
    sort_diff = sorted(diff)
    ans = 0
    for i in range(N-K):
        ans += sort_diff[i]

    print(ans)



if __name__ == "__main__":
    main()