**Problem links:**

Contest

Practice

**Difficulty:**

Cakewalk

**Prerequisites:**

Math, Permutation and combination

**Problem:**

The aim is to find the number of quadrilaterals in a grid containing m horizontal lines and n vertical lines. In this case, the quadrilaterals will only be squares or rectangles which will be given by (nC2*mC2).

**Explanation:**

To make a rectangle or a square from given m horizontal lines and n vertical lines we need to select 2 lines out of m horizontal lines and 2 lines out of n vertical lines.

Number of ways in which we can select 2 horizontal lines out of n = nC2

=(n)!/((n-2)!$*2)
=(n*$(n-1))/2.

Number of ways in which we can select 2 vertical lines out of m = mC2

= (m)!/((m-2)!$*2)
= (m*$(m-1))/2.

To make a rectangle or a square we need to select 2 vertical and 2 horizontal lines simultaneously, so, the answer will be (nC2*mC2).

**Solution:**

#include using namespace std; int main() { unsigned long long t,n,m; cin>>t; while(t) { cin>>n>>m; cout<<(n*(n1)/2)*(m*(m1)/2)<<endl; } return 0; }