C++ Trapezoidal Rule

Implementation of Trapezoidal Rule (Integral Approximation) written in C++.

Enter begining of interval: -2
Enter end of interval: 2
Enter number of iterations: 1000000
Integral is equal to: 5.33335

#include <iostream>

// ? 2018 TheFlyingKeyboard and released under MIT License 
// theflyingkeyboard.net

using namespace std;

double function(double x);

int main() {
  double intervalBegin;
  double intervalEnd;	
  int count;
  double integral;
  double step;

  cout << "Enter begining of interval: "; 
  cin >> intervalBegin; 

  cout << "Enter end of interval: "; 
  cin >> intervalEnd;

  cout << "Enter number of iterations: "; 
  cin >> count;

  step = (intervalEnd - intervalBegin) / count;
  integral = 0.5 * (function(intervalBegin) + function(intervalEnd));

  for (int i = 0; i < count; ++i) {
    integral += function(intervalBegin + step * i);
  }

  integral *= step;
  cout << "Integral is equal to: " << integral << endl;

  int a;
  cin >> a;

  return 0;
}

double function(double x) {
  return x * x;
}