a = [0]*80

f = open('fileB1.txt')

n = int(f.readline())

for i in range(0,n):
    x = int(f.readline())
    a[x % 80] += 1

s = a[0]*(a[0]-1)//2 + a[40]*(a[40]-1)//2

for i in range(1, 41):
    s += a[i]*a[80-i]

print(s)