sm = input()
m = []
s = 0
am = 0
for i in range(12):
    m.append(list(map(float,input().split())))
a = 0
b = 5
for i in range(0,6):
    for j in range(a):
        s += m[i][j]
        am += 1
    a += 1

for i in range(6,11):
    for j in range(b):
        s += m[i][j]
        am += 1
    b -= 1


if sm == 'S':
    print("%.1lf"%s)
elif sm == 'M':
    print("%.1lf"%(s/am))