#include<bits/stdc++.h>
using namespace std;
int a[10000000];
int b[10000000];
int main(){
	int n,num=0,sum;       
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		cin>>b[i];
		sum=(a[i]+b[i])-8;
		num=num+sum;
	}
	cout<<num;
	return 0;
}