#include <cstdio>
#include <algorithm>

const int maxN = 100100;
const int baza = 200000;
const int mod = 666013;

using namespace std;

char s[10 * maxN];
int V[maxN], D[maxN];
int h1[maxN], h2[maxN], powerB[maxN];
int N, rez;

int main() {
	int i, j;
	freopen("numarare.in", "r", stdin);
	freopen("numarare.out", "w", stdout);

	scanf("%d ", &N);
	for (i = 1; i <= N; i++)
		scanf("%d", &V[i]);
/*	fgets(s, 1000000, stdin);

	j = s[0];
	for (i = 1; i <= N; i++) {
		while (s[j] >= '0' && s[j] <= '9') {
			V[i] = V[i] * 10 + (s[j] - 48);
			j++;
		}

		while (s[j] < '0' || s[j] > '9')
			j++;
	}*/

	for (i = 1; i < N; i++) {
		D[i] = V[i] - V[i + 1] + 200000;
//		fprintf(stderr, "%d ", D[i]);
	}
//	fprintf(stderr, "\n");

	for (i = 1; i < N; i++) {
		h1[i] = (1LL * h1[i - 1] * baza + D[i]) % mod;
//		fprintf(stderr, "%d ", h1[i]);
	}
//	fprintf(stderr, "\n");

	for (i = N - 1; i > 0; i--) {
		h2[i] = (1LL * h2[i + 1] * baza + D[i]) % mod;
//		fprintf(stderr, "%d ", h2[i]);
	}
//	fprintf(stderr, "\n");

	powerB[0] = 1;
	for (i = 1; i <= N; i++)
		powerB[i] = (1LL * powerB[i - 1] * baza) % mod;


	for (i = 1; i < N; i++) {
		int left, right, m, sol = 0;
		left = 1; right = min(i, N - i - 1);

		while (left <= right) {
			m = (left + right) / 2;
			//o sa am de la i - m  la i + m 

			int R1, R2;
			R1 = h1[i] - (1LL * h1[i - m - 1] * powerB[m + 1] % mod);
			if (R1 < 0)	R1 += mod;

			R2 = h2[i] - (1LL * h2[i + m + 1] * powerB[m + 1] % mod);
			if (R2 < 0)	R2 += mod;

/*			if (i == 4) {
				fprintf(stderr, "%d   %d %d\n", m, R1, R2);
			}*/

			if (R1 == R2) {
				left = m + 1;
				sol = m;
			}
			else
				right = m - 1;
		}

//		fprintf(stderr, "%d   %d\n", i, sol);

		rez = rez + sol + 1;
	}

	printf("%d\n", rez);


	return 0;
}