The diver's log

Problem

Underwater, the time matters less than the depth, and Irene's watch keeps track of it: a - for every meter she goes down and a + for every meter she comes up. A dive starts when she leaves the surface and ends when she gets back to it; any ups and downs in between, without surfacing, belong to the same dive.

Write a function that takes the day's log, a string of - and +, and returns how many dives she made (a whole number). The log always starts and ends at the surface, and never goes above it. With "--+-++" she goes down 2, up 1, down 1 and up 2: she surfaces only once, so it is 1 dive. With "-+-+" it is 2. An empty log is a day without diving: 0.

Examples

• The example

  "--+-++" → 1

• Two short dives

  "-+-+" → 2

• A single dive, straight down and up

  "---+++" → 1

• Three dives of different depths

  "-+--++-+" → 3

Besides these, the challenge has hidden tests that are revealed when you submit your solution.

You start with this

def dives(log):
    pass

function dives(log) {
}