codeforces/cpp/467A.cpp

#include <iostream>

using namespace std;

int main()
{
    int n;
    cin >> n;
    int sum = 0;
    while (n--)
    {
        int p, q;
        cin >> p >> q;
        if (q - p >= 2)
        {
            sum++;
        }
    }
    cout << sum;
    return 0;
}