What is the output of following code segment?

def foo$($arr$,x)$:

for $i$ in range$($len$($arr$))$:

if arr$[i]==x$ :

return $i$

return $-1$

$a=[0,2,4,6,8]$

print$($foo$($a$,2))$

$1$

Error

$2$

$4$