Sprinter

n = int(input())
timeDistanceList = []
for i in range(0,n):
    timeDistanceList.append(input().split())

timeDistanceList.sort()
#print(timeDistanceList)

#find fastest rate
greatestRate = 0
tempList = []
for i in timeDistanceList:
    tempList = timeDistanceList
    tempList.remove(i)
    for t in tempList:
        changeInMeters = abs(int(i[1]) - int(t[1]))
        changeInSeconds = abs(int(i[0]) - int(t[0]))
        if (changeInMeters/changeInSeconds) > greatestRate:
            greatestRate = (changeInMeters/changeInSeconds)

print(greatestRate)