#include <bits/stdc++.h>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> vec;
    for (int i = 0; i < n; i++) {
        int c;
        cin >> c;
        vec.push_back(c);
    }
    int count = 0;
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
            if (abs(vec[i] - vec[j]) == 1) {
                count++;
            }
        }
    }
    cout << count << endl;
    return 0;
}