#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,sum,cnt;
signed main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		int y,x1,x2;
		cin>>y>>x1>>x2;
		sum+=y*2;
		if(i!=n){
			cnt+=y;
		}
	}
	cout<<sum-cnt;
	return 0;
}

AC 第2个点