#include<bits/stdc++.h>
using namespace std;
struct{
	int e,c,m;
}a[100]; 
int main(){
	int n,t=0;
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>a[i].e;
		cin>>a[i].c;
		cin>>a[i].m;
	}
	for(int i=0;i<n-1;i++){
		if(-5<=a[i].e-a[i+1].e<=5){
			if(-5<=a[i].c-a[i+1].c<=5){
				if(-5<=a[i].m-a[i+1].m<=5){
					t++;
				}
			}
	
		}
	}
	cout<<t;
	return 0;
}