#include <iostream>
#include <iomanip>
using namespace std;
long long n;
long long sum = 0;
long long jing;
long long a,b;
int main(){
	cin>>n;
	for (long long i = 1;i <= n;i++){
		cin>>a>>b;
		jing = a + b - 8;
		sum += jing;
	}
	cout<<sum<<endl;
	return 0;
}

20分求大佬帮助！！！！！！！！