Draw lines and number those lines. You will find the pattern soon.

The `i-th`

can only cross `i-3th`

, `i-4th`

or `i-5th`

on the first crossing.

```
class Solution(object):
def isSelfCrossing(self, x):
"""
:type x: List[int]
:rtype: bool
"""
if len(x) < 4:
return False
for i in range(3, len(x)):
if x[i] >= x[i-2] and x[i-1] <= x[i-3]:
return True
if i >= 4 and x[i-1] == x[i-3] and x[i] + x[i-4] >= x[i-2]:
return True
if i >= 5 and x[i-1] <= x[i-3] and x[i-3] <= x[i-1] + x[i-5] and x[i] + x[i-4] >= x[i-2] and x[i-4] <= x[i-2]:
return True
return False
```