sensor question

[CruisinSpeed6]

So, I'm a little confused on sensor location.
I got two CELs: P0031 and P0134, the code reads as the front O2 sensor.
Is this the sensor that's at the bottom of the DP or at the top closer to the engine? Any input? Thanks

 

[wannabe]

should be the first one in the exhaust system.

 

[CruisinSpeed6]

should be the first one in the exhaust system.

ok, at the top or bottom?
[edit] top