#include <iostream>
using namespace std;

int main()
{
  int b, c;

  cout << "(If it isn't completely numerical, the answer will be varying.)\n(The answer will also vary if the numbers are too large.)" << endl;
  cout << "This was created and coded by Luang Cui." << endl;
  cout << "Thanks to my father for the mathematical formula." << endl;
  cout << "Please, enter a smaller integer first, then a larger integer." << endl;
  char question[] = "First integer: ";
  int a;
  cout << question;
  cin >> a;
  char question2[] =  "Second integer: ";
  int d;
  cout << question2;
  cin >> d;
  if (a<d)
  {
          char answer[] = "Output, ";

  b= d;
  c= ((a + b) * ((b - a) + 1)) / 2;

  cout << answer << c << "." << endl;
  cout << "The output is reached by a special mathematical formula." << endl;
  cout << "The pattern adds 1 to the smaller integer continuously until the next integer is equal to the larger integer." << endl;
  cout << "EXAMPLE: 1+2+3...+100." << endl;
  cout << "The formula is: {(X+Y)*[(Y-X)+1]}/2, where X is the smaller integer and Y is the larger." << endl;
  }
   else
    {
          cout << "The first integer is larger than or equal to the second!" << endl;
    }
  system("PAUSE");
  return 0;
}

  char question[] = "First integer: ";
  cout << question;

  cout << "First integer: ";

char question[] = "First integer: ";