```
a = [1,2,3,4,5,6,7,8,9]
b = [10,11,12,13,14,15,16,17,18,19]
def p(x):
return len(x) % 2 * 1
def px(x):
n = len(x) // 2
m = n - 1
if p(x):
n += 1
return (m, n) if m > -1 else []
```

Without dependency,

```
def px(x):
p = lambda x: len(x) % 2 * 1
n = len(x) // 2
m = n - 1
if p(x):
n += 1
return (m, n) if m > -1 else []
```