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#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1e6+10;
int a,b,n,ans;
int main()
{
cin >> n;
for (int i = 0; i < n; i ++ )
{
scanf("%d%d", &a, &b);
if(b-a>=2)
{
ans++;
}
}
cout << ans;
return 0;
}