LastProblem.cpp

#include<bits/stdc++.h>
using namespace std;

int findnum(int x1, int y1){  //function that returns the element with an index
    
    int sum1=1;
    for(int i=0;i<(x1-1);i++){
        sum1=sum1+(2+i);
    }
    
    int sum2=sum1;
    int j=y1-1;
    int i=x1;
    while(j--){
        sum2=sum2+i;
        i++;
    }
    return sum2;
}
int main()
{
   int tcase;
   cin>>tcase;
   
  while(tcase--){
      int x1,x2,y1,y2;
      cin>>x1>>y1>>x2>>y2;
      int sumf=findnum(x1,y1);
      while(x1<x2){  //going down
          x1++;
          sumf+=findnum(x1,y1);
          
          
      }
      while(y1<y2){  //going right
          y1++;
          sumf+=findnum(x1,y1);
      }
    cout<<sumf<<endl;     
  } 
   return 0;
}