#include <iostream>
#include <unordered_map>
#include <vector>

int count_asakatsu_subsequences(int N, std::vector<int>& A) {
    int cnt = 0;
    std::unordered_map<int, std::vector<int>> indices;

    for (int i = 0; i < N; i++) {
        int a = A[i];
        indices[a].push_back(i);
    }

    for (int i = 0; i < N - 3; i++) {
        for (int j = i + 1; j < N - 2; j++) {
            int k = A[j] - A[i] - 10;
            if (k > 0) {
                std::vector<int>& m_values = indices[A[j] - k];
                for (int m : m_values) {
                    if (m > j) {
                        std::vector<int>& n_values = indices[A[m] + k + 1];
                        for (int n : n_values) {
                            if (n > m) {
                                cnt++;
                            }
                        }
                    }
                }
            }
        }
    }

    return cnt;
}

int main() {
    int N;
    std::cin >> N;
    std::vector<int> A(N);
    for (int i = 0; i < N; i++) {
        std::cin >> A[i];
    }

    int result = count_asakatsu_subsequences(N, A);

    std::cout << result << std::endl;

    return 0;
}