##### Short Problem Definition:

Sami’s spaceship crashed on Mars! She sends a series of `SOS`

messages to Earth for help.

##### Link

##### Complexity:

time complexity is `O(N)`

space complexity is `O(1)`

##### Execution:

We know that the message is basically a lot of concatenated SOS strings. There is no magic to this one.

##### Solution:

```
S = raw_input().strip()
errors = 0
for i in xrange(len(S)):
if i % 3 == 0 and S[i] != 'S':
errors += 1
if i % 3 == 1 and S[i] != 'O':
errors += 1
if i % 3 == 2 and S[i] != 'S':
errors += 1
print errors
```