#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;

int main() {
    int N;
    cin >> N;

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

    unordered_map<int, vector<int>> di;
    for (int i = 0; i < N; ++i) {
        di[A[i]].push_back(i);
    }

    int ans = 0;
    for (int i = 0; i < N - 3; ++i) {
        for (int j = i + 1; j < N - 2; ++j) {
            if (di.find(A[i] + 10) != di.end()) {
                for (int k : di[A[i] + 10]) {
                    if (A[k] > A[j]) break;
                    if (di.find(A[j] + 1) != di.end()) {
                        for (int l : di[A[j] + 1]) {
                            if (A[i] + 10 == A[k] && A[j] + 1 == A[l] && A[i] < A[j] && A[j] > A[k] && A[k] < A[l] && i < j && j < k && k < l) {
                                ans++;
                            }
                        }
                    }
                }
            }
        }
    }

    cout << ans << endl;

    return 0;
}