#include <iostream>

int main()
{
  int operation;
  float first, second;
  
  cout << "First number? ";
  cin >> first;
  
  cout << "Second number? ";
  cin >> second;
  
  cout << "1. addition" << endl
       << "2. subtraction" << endl
       << "Operation? ";
  cin >> operation;
  
  switch (operation)
  {
    case 1:
      cout << first + second << endl;
      break;
    case 2:
      cout << first - second << endl;
      break;
    default:
      cout << "Not a valid operation" << endl;
  }
  
  return 0;
  
}

/*
/homes/home30/hkim16/107> a.out
First number? 6
Second number? 4
1. addition
2. subtraction
Operation? 1
10
/homes/home30/hkim16/107> a.out
First number? 6
Second number? 4
1. addition
2. subtraction
Operation? 2
2
/homes/home30/hkim16/107> a.out
First number? 6
Second number? 4
1. addition
2. subtraction
Operation? 3
Not a valid operation
*/