Hello, new to python a bit. I get an indentation error at line 10, "m -= 1". Sorry if this is a repeated post, I've tried searching but found no solution.

```
# calculates sum of squares of natural numbers
print "Enter number of terms."
n = raw.input("Terms? ")
first_term = ( ( n * n + n ) / 2 ) - 1
m = n
if m != 0:
b = m * m + m
m -= 1
a = b
while m! = 0:
a = b
b = m * m + m
m -= 1
a = a + b
else:
break
second_term = a
third_term = 1
answer = first_term + second_term + third_term
print answer
```