Buggy python submission (verdict: Time Limit Exceeded):
import itertools
n = int(input())
a = list(map(int, input().split()))
idList = [i for i in range(1, n+1)]
'''
com = list(itertools.combinations(idList, 2))

num = len(com)
'''
ans = 0

for i in range(1, n + 1):
    for j in range(i + 2, n + 1):
        key = j - i
        heiA = a[i - 1]
        heiB = a[j - 1]
        height = heiA + heiB
        if (height == key):
            ans += 1

print(ans)
'''
for i in range(num):
    aa = com[i]
    # print(aa)
    idA = aa[0]
    idB = aa[1]
    dif = abs(idA - idB)
    indexA = idList.index(idA)
    indexB = idList.index(idB)

    height = a[indexA] + a[indexB]

    if (height == dif):
        ans += 1

print(ans)
'''


Fixed submission:
from collections import Counter
N = int(input())
A = list(map(int, input().split()))

minus = [0] * N
plus = [0] * N

for i in range(N):
    minus[i] = (i + 1) - A[i]
    plus[i] = (i + 1) + A[i]

count = Counter(minus)
most = count.most_common()
num = len(most)

countPP = Counter(plus)
#mostPP = countPP.most_common()
#check = mostPP[:][0]
ans = 0

for i in range(num):
    elm = most[i]
    fir = elm[0]
    sec = elm[1]
    # if (fir in check):

    aa = countPP[fir]
    #    print(aa)
    ans += aa * sec

    # try countPP[tar]:

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import itertools
n = int(input())
a = list(map(int, input().split()))
idList = [i for i in range(1, n+1)]
temp = 0
for i in range(n):
    tar = a[temp]
    if (tar >= n):
        del a[temp]
        del idList[temp]

    else:
        temp += 1

com = list(itertools.combinations(idList, 2))

num = len(com)
ans = 0
for i in range(num):
    aa = com[i]
    # print(aa)
    idA = aa[0]
    idB = aa[1]
    dif = abs(idA - idB)
    indexA = idList.index(idA)
    indexB = idList.index(idB)

    height = a[indexA] + a[indexB]

    if (height == dif):
        ans += 1

print(ans)


Fixed submission:
from collections import Counter
N = int(input())
A = list(map(int, input().split()))

minus = [0] * N
plus = [0] * N

for i in range(N):
    minus[i] = (i + 1) - A[i]
    plus[i] = (i + 1) + A[i]

count = Counter(minus)
most = count.most_common()
num = len(most)

countPP = Counter(plus)
#mostPP = countPP.most_common()
#check = mostPP[:][0]
ans = 0

for i in range(num):
    elm = most[i]
    fir = elm[0]
    sec = elm[1]
    # if (fir in check):

    aa = countPP[fir]
    #    print(aa)
    ans += aa * sec

    # try countPP[tar]:

print(ans)

Buggy python submission (verdict: Runtime Error):
import itertools
n = int(input())
a = list(map(int, input().split()))
idList = [i for i in range(1, n+1)]
temp = 0
for i in range(n):
    tar = a[temp]
    if (tar >= n):
        del a[i]
        del idList[i]

    else:
        temp += 1

com = list(itertools.combinations(idList, 2))

num = len(com)
ans = 0
for i in range(num):
    aa = com[i]
    # print(aa)
    idA = aa[0]
    idB = aa[1]
    dif = abs(idA - idB)
    indexA = idList.index(idA)
    indexB = idList.index(idB)

    height = a[indexA] + a[indexB]

    if (height == dif):
        ans += 1

print(ans)


Fixed submission:
from collections import Counter
N = int(input())
A = list(map(int, input().split()))

minus = [0] * N
plus = [0] * N

for i in range(N):
    minus[i] = (i + 1) - A[i]
    plus[i] = (i + 1) + A[i]

count = Counter(minus)
most = count.most_common()
num = len(most)

countPP = Counter(plus)
#mostPP = countPP.most_common()
#check = mostPP[:][0]
ans = 0

for i in range(num):
    elm = most[i]
    fir = elm[0]
    sec = elm[1]
    # if (fir in check):

    aa = countPP[fir]
    #    print(aa)
    ans += aa * sec

    # try countPP[tar]:

print(ans)

Buggy python submission (verdict: Runtime Error):
import itertools
n = int(input())
a = list(map(int, input().split()))
idList = [i for i in range(1, n+1)]
temp = 0
for i in range(n):
    tar = a[temp]
    if (tar >= n):
        del a[i]
        del idList[i]

    else:
        temp += 1

com = list(itertools.combinations(idList, 2))

num = len(com)
ans = 0
for i in range(num):
    aa = com[i]
    # print(aa)
    idA = aa[0]
    idB = aa[1]
    dif = abs(idA - idB)
    height = a[idA - 1] + a[idB - 1]

    if (height == dif):
        ans += 1

print(ans)


Fixed submission:
from collections import Counter
N = int(input())
A = list(map(int, input().split()))

minus = [0] * N
plus = [0] * N

for i in range(N):
    minus[i] = (i + 1) - A[i]
    plus[i] = (i + 1) + A[i]

count = Counter(minus)
most = count.most_common()
num = len(most)

countPP = Counter(plus)
#mostPP = countPP.most_common()
#check = mostPP[:][0]
ans = 0

for i in range(num):
    elm = most[i]
    fir = elm[0]
    sec = elm[1]
    # if (fir in check):

    aa = countPP[fir]
    #    print(aa)
    ans += aa * sec

    # try countPP[tar]:

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import itertools
n = int(input())
a = list(map(int, input().split()))
idList = [i for i in range(1,n+1)]

com = list(itertools.combinations(idList, 2))

num = len(com)
ans = 0
for i in range(num):
    aa = com[i]
    # print(aa)
    idA = aa[0]
    idB = aa[1]
    dif = abs(idA - idB)
    height = a[idA - 1] + a[idB - 1]

    if (height == dif):
        ans += 1

print(ans)


Fixed submission:
from collections import Counter
N = int(input())
A = list(map(int, input().split()))

minus = [0] * N
plus = [0] * N

for i in range(N):
    minus[i] = (i + 1) - A[i]
    plus[i] = (i + 1) + A[i]

count = Counter(minus)
most = count.most_common()
num = len(most)

countPP = Counter(plus)
#mostPP = countPP.most_common()
#check = mostPP[:][0]
ans = 0

for i in range(num):
    elm = most[i]
    fir = elm[0]
    sec = elm[1]
    # if (fir in check):

    aa = countPP[fir]
    #    print(aa)
    ans += aa * sec

    # try countPP[tar]:

print(ans)