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i.py

@@ -0,0 +1,17 @@
+from __future__ import print_function
+import sys
+
+m, s    = map(int, sys.stdin.readline().split())
+prefs   = [ map(int, line.split()) for line in sys.stdin ]
+inits   = [ set() for x in xrange(m) ]
+answer  = set()
+
+for j in xrange(s):
+  for i in xrange(m): answer.add(prefs[i][j])
+  all_ok = True
+  for i in xrange(m):
+    inits[i].add(prefs[i][j])
+    if len(inits[i]) != len(answer): all_ok = False
+  if all_ok: break
+  
+print(len(answer)); print(" ".join(map(str, sorted(answer))))