Codeforces Round 389 Div.2 B. Santa Claus and Keyboard Check(模拟)
B.SantaClausandKeyboardCheck原题链接:http://codeforces.com/problemset/problem/748/BSantaClausdecidedtodisassemblehiskeyboardtocleanit.Afterhereturnedallthekeysback,hesuddenlyrealizedthatsomepairsofkeystoo