broken multi threaded counter

Broken counter

What's the minimum value this Python code can print:

Given 5 threads that each increment an integer counter variable exactly 10 times. The variable isn't guarded by any lock. You can assume that reading and writing to the variable are atomic operations. What's the minimum value the counter can have after all threads finished.
 
In Python it would look like this:
== code(c) |

== code(python) |

import threading
num_threads = 5

threads = []
for i in xrange(0, num_threads):

  threads.append(threading.Thread(target=increment, args=(count,)))

  threads.append(threading.Thread(
                   target=increment,
                   args=(count,)))

for t in threads:
   t.start()

print counter
==

The puzzle asks for the minimum value this code can print.
 

The fact that the code is in Python doesn't really matter. Basically you're given 5 threads that each increment an integer variable _counter_ exactly 10 times. The variable isn't guarded by any lock. You can assume that reads and writes to the variable are atomic operations. What's the minimum value the counter can have after all threads finished.

private

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