2.Duplicate Pair http://acm.fzu.edu.cn/problem.php?pid=1001 import sys while True: line=sys.stdin.readline() if not line: break line=[int(x) for x in line.rstrip().split( )] if len(line)>1: line.sort() for i in range(0,len(line)): if line[i]==line[i+1]: print(line[i]) break