import sys
n = int(sys.stdin.readline().strip())
a = list(map(int,sys.stdin.readline().split()))
d = {}
for i in range(n):
x = a[i] -i
d[x] = d.get(x,0) + 1
m = 0
for i in d.values():
m += i*(i-1)//2
print(m)

import sys
n = int(sys.stdin.readline().strip())
a = list(map(int,sys.stdin.readline().split()))
d = {}
for i in range(n):
x = a[i] -i
d[x] = d.get(x,0) + 1
m = 0
for i in d.values():
m += i*(i-1)//2
print(m)