def solve_new(l, k, d):
    d = [int(n) for n in d]
    d.sort(key=int)
    diff = []
    for i in range(len(d) - 1):
        diff.append(d[i+1] - d[i])
    return sum(sorted(diff)[:len(d) - k])

if __name__ == '__main__':
    l, k = map(int, input().split())
    print(solve(l, k, input().split()))