Not quite as short as the others. It's on one line on account of the wiki.
muriel:Desktop rburns$ ls -l golf.io -rw-r—r—@ 1 rburns staff 147 Oct 27 16:28 golf.io
R := File standardInput readLines map(split map(asNumber)); C := list; for(i,0,9,C append(R map(at(i)))); list(R,C) map(map(sum)) flatten max println
R := File standardInput readLines map(split map(asNumber)); C := list; for(i,0,9,C append(R map(at(i)))); list(R,C) map(map(sum)) flatten max println
I think yours might be the first that actually reads from stdin though.