func main()
	var N: int :: cui@input().toInt(&)
	var ans: int
	for(1, N)
		var ss: [][]char :: cui@input().split(" ")
		var HM: [][]char :: ss[0].split(":")
		var hm: [][]char :: ss[1].split(":")
		var H: int :: HM[0].toInt(&)
		var M: int :: HM[1].toInt(&)
		var h: int :: hm[0].toInt(&)
		var m: int :: hm[1].toInt(&)
		do ans :+ (h * 60 + m - H * 60 - M + 1440) % 1440
	end for
	do cui@print("\{ans}\n")
end func