Codeforces_467A

//Codeforces Round 467A
#include <iostream>
using namespace std;
int main()
{
    int n, p, q, answ=0;
    cin >> n;
    for(int i=0;i<n;i++)
    {
        cin >> p >> q;
        if((q-p)>=2){answ++;}
    }
    cout << answ;
    return 0;
}