func main()
	var N: int :: cui@input().toInt(&)
	var ans: int
	for(1, N)
		var _: [][]char :: cui@input().split(" ")
		var _0: [][]char :: _[0].split(":")
		var _1: [][]char :: _[1].split(":")
		var H: int :: _0[0].toInt(&)
		var M: int :: _0[1].toInt(&)
		var h: int :: _1[0].toInt(&) + 24
		var m: int :: _1[1].toInt(&)
		do ans :+ (h * 60 + m - H * 60 - M) % 1440
	end for
	do cui@print("\{ans}\n")
end func