n = int(raw_input())
s = 0
for _ in range(n):
    i,j = raw_input().split('.')
    s += int(i) * (10**10)
    if i[0] == '-':
        s -= int(j) * (10**(10-len(j)))
    else:
        s += int(j) * (10**(10-len(j)))
print str(s/(10**10)) + '.' + str(s%(10**10)).zfill(10)