mean velocity

vct=600*[0]
for i in range(600):
    vct[i]=int(input())
b=10*[0]
for i in range(600):
    if i<60:
        b[0]=b[0]+vct[i]
    elif i<120:
        b[1]=b[1]+vct[i]
    elif i<180:
        b[2]=b[2]+vct[i]
    elif i<240:
        b[3]=b[3]+vct[i]
    elif i<300:
        b[4]=b[4]+vct[i]
    elif i<360:
        b[5]=b[5]+vct[i]
    elif i<420:
        b[6]=b[6]+vct[i]
    elif i<480:
        b[7]=b[7]+vct[i]
    elif i<540:
        b[8]=b[8]+vct[i]
    elif i<600:
        b[9]=b[9]+vct[i]
for i in range(10):
    b[i]=b[i]/60
a=b[0]
for i in range(1,10):
    if b[i]>a:
        a=b[i]
print(a)