resposta errada op = input()

M = [] for i in range(12): linha = [] for j in range(12): linha.append(float(input())) M.append(linha) x = 0 soma = 0.0 for l in range(11): p = l for i in range(p): soma += M[l+1][i]

    x += 1

if op == 'S': print("{:.1f}".format(soma)) else: print("{:.1f}".format(soma/x))