C. Celex Update--------------------------------思維

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll a,b,c,d;
int t;
int main()
{
	cin>>t;
	while(t--)
	{
		cin>>a>>b>>c>>d;
		cout<<abs(c-a)*abs(d-b)+1<<endl;
	}
}