Error:

Oops, try again. Your function fails on is_prime(4). It returns True when it should return False.

```
def is_prime(x):
if x < 2:
return False
elif x == 2 or x == 3:
return True
else:
for n in range(2, (x - 1)):
if x % n == 1:
return False
else:
return True
```