#include <iostream>
#include <utility>
#include <vector>
#include <algorithm>

int main() {
    int n, m;
    std::vector< std::pair<int, int> > A;
    
    std::cin >> n >> m;
    A.reserve(n);
    for (int i = 0; i < n; i++) {
        int b, c;
        std::cin >> b >> c;
        A.emplace_back(b, c);
    }

    std::sort(A.begin(), A.end(), [](std::pair<int, int>& a, std::pair<int, int>& b) {
        return a.second == b.second ? a.first < b.first : a.second < b.second;
    });

    int cnt = 0;
    for (int i = 0; i < n - 1; i++) {
        if (A[i].second == A[i+1].second && A[i].first != A[i+1].first) {
            cnt++;
        }
    }

    std::cout << cnt << std::endl;
    
    return 0;
}