n, m = read_line.split.map(&.to_i)
l = [-(1 << 30)] + read_line.split.map(&.to_i) + [1 << 30]
ans = 0i64
m.times do
  f, b, w = read_line.split.map(&.to_i)
  pos = l.bsearch_index { |x, i| x >= f }.not_nil!
  dist = {l[pos] - f, f - l[pos - 1]}.min
  ans += {b, w - dist}.max
end
puts ans