Kata

You need count how many valleys you will pass.

Start is always from zero level.

Every time you go down below 0 level counts as an entry of a valley, and as you go up to 0 level from valley counts as an exit of a valley.

One passed valley is equal one entry and one exit of a valley.

s='FUFFDDFDUDFUFUF'
U=UP
F=FORWARD
D=DOWN

To represent string above

(level 1)  __
(level 0)_/  \         _(exit we are again on level 0)
(entry-1)     \_     _/
(level-2)       \/\_/

So here we passed one valley