Very Simple Triangles Write a program or function that takes in a positive integer (via stdin, command line, or function arg) and prints or returns a string of that many of these small triangles tiled together, alternating which way they point:

 /\
/__\


This sole triangle is the output if the input is 1.

If the input is 2, the output is

  ____
 /\  /
/__\/


If the input is 3, the output is

  ____
 /\  /\
/__\/__\


If the input is 4, the output is

  ________
 /\  /\  /
/__\/__\/


And so on. Your program must support inputs up to 216 - 1 = 65535.

Details


The leftmost triangle always points upwards.
There may be trailing spaces but there may not be unnecessary leading spaces.
There may be an optional trailing newline.
Note that for 1 the output is two lines long but otherwise it's three. This is required.
The shortest submission in bytes wins.
Pyth, 44 42

ItQpdd*\_*4/Q2)jbms&lt;*dQhQ,c" /\ "2,\/"__\\


The first line:

ItQpdd*\_*4/Q2)
ItQ           )    If the input is not 1
   pdd             Print two spaces
      *\_*4/Q2     Then groups of 4 underscores, repeated input/2 times.


The other two lines are generated by noticing that the second line consists of " /" and "\ " alternating input + 1 times, and the third line consists of "/" and "__\" alternated in the same fashion.