link: http://mirror.codeforces.com/problemset/problem/457/E

"If the intern's solution may be optimal, print the efficiency of the solution if it can be determined rounded to the nearest integer, otherwise print "UNKNOWN"."

I think the efficienty of the solution is always undetermined,because if intern's solution is correct,and total flow is k,for every correct solution we can always add a new eddge from node 1 to node n with w==inf and b==1,the total flow is k+1 and intern's solution is also correct for optimal cost,but the effiency is surely changed.

am I miss something?