def proc(data,m):
    n=len(data)
    queinfo=[[0 for i in range(n)] for j in range(m)]
    head=[0]*m
    tail=[0]*m
    curtime=0
    waitnum=0
    i=0
    total=0
    while i<n or waitnum>0:
        if i<n and data[i][0]<=curtime:
            k=data[i][2]
            __________
            tail[k]+=1
            waitnum+=1
            i+=1
        elif waitnum>0:
            k=0
            while __________:
                k+=1
            __________
            head[k]+=1
            total+=curtime-data[p][0]
            curtime+=data[p][1]
            waitnum-=1
        else:
            __________
    return "%.4f"%(total/n) 

n=int(input())
data=[]
for i in range(n):
    data.append(list(map(int,input().split())))
print(proc(data,4))