n = int(input())
vals = []
speeds = []
for i in range(n):
    inpt = list(map(int, input().split(" ")))
    vals.append(inpt)

vals = sorted(vals)

for i in range(len(vals)-1):
    speeds.append(abs(vals[i][1] - vals[i+1][1])/abs(vals[i][0]- vals[i+1][0]))

speeds = sorted(speeds)
print(speeds[-1])