#include<bits/stdc++.h>
using namespace std;
int n , a[100000] , b[100000] , sum = 0 ;
int main(){
	cin >> n;
	for(int i = 1 ; i<= n ;i ++){
		cin >> a[i] >> b[i];
		int no = a[i] + b[i];
		if(no > 8){
			sum -= no - 8;
		}else{
			sum += 8 - no;
		}
	}
	cout << sum;
	return 0;
}

555