mod = 5673201419
base = 7
base_ = pow(base, -1, mod)
n = int(input())
A = list(map(int, input().split()))
"""
n = 10 ** 6
from random import randrange as R
A = [R(1, 10**9) for i in range(n)]
"""
B = [0] * n
for i in range(n-1):
    a = A[i+1]-A[i]
    B[i+1] = (B[i]*base+a)%mod
C = [0] * n
for i in range(n-2, -1, -1):
    a = A[i+1]-A[i]
    C[i] = (C[i+1]*base+a)%mod

D = [1] * n
for i in range(n-1):
    D[i+1] = D[i]*base % mod

def check(l0, r0, l1, r1):
    a = (B[r0-1] - B[l0] * D[r0-l0-1]) % mod
    b = (C[l1] - C[r1-1] * D[r1-l1-1]) % mod
    return a == b

ans = 0
for i in range(n):
    r = min(i+1, n-i)+1
    l = 1
    while r - l > 1:
        m = (l + r) >> 1
        if check(i+1-m, i+1, i, i+m):
            l = m
        else:
            r = m
    ans += l

for i in range(n-1):
    r = min(i+1, n-i-1)+1
    l = 1
    while r - l > 1:
        m = (l + r) >> 1
        if check(i+1-m, i+1, i+1, i+1+m):
            l = m
        else:
            r = m
    ans += l

print(ans)