#include<bits/stdc++.h>
using namespace std;
int n;
int main(){
	int a,b,sum[3030],ans;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a>>b;
		sum[i]=(sum[i-1]+a+b)-8;
		ans+=sum[i];
	}
	cout<<ans;
	
	
	
	return 0;
}