#include <bits/stdc++.h>
using namespace std;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	int total = 0;
	string line;
	while (getline(cin, line) && !line.empty()) {
		istringstream l(line);
		vector<int> t;
		while (!l.eof()) {
			int x;
			l >> x;
			t.push_back(x);
		}
		int pos = (t[1] > t[0]) ? 1 : -1;
		for (int i = 0; i < t.size() - 1; i++) {
			int diff = (t[i + 1] - t[i]) * pos;
			if (diff < 1 || diff > 3) {
				goto next;
			}
		}
		total++;
	next:;
	}
	cout << total << '\n';
}