#include <stdio.h>

double a=0,s=0,m=0,d=0;
int g=0;

/* Function declarations */
double add(double a, double b);

/* Function definitions */
double add(double a, double b)
{
 double a1=a+b;
 return a1;
}

double subtract(double a,double b)
{
 double s = a-b;
 return s;
}

double multiply(double a, double b)
{
 double m = a*b;
 return m;
}

double divide(double a,double b)
{
 double d = a/b;
 return d;
}

int gcd(int a,int b)
{
  int t=0;
  while(b!=0)
  {
    t = b;
    b = a%b;
    a = t;
  }
  g = a;
  return g;
}

int main(void)
{
  double a=0,s=0,m=0,d=0,x=0,y=0;
  int g =0;
  int option;

  while(1)
  {

  printf("******* Calculator ********\n");
  printf("1: Add 2 numbers\n");
  printf("2: Subtract 2 numbers\n");
  printf("3: Multiply 2 numbers\n");
  printf("4: Divide 2 numbers\n");
  printf("5: GCD of 2 numbers\n");
  printf("6: Quit\n");

  printf("Enter choice from 1-5, 6 to quit: ");
  scanf("%d",&option);

  if(option<6)
  {
    printf("Enter first number: ");
    scanf("%lf",&x);
    printf("Enter second number: ");
    scanf("%lf",&y);
  }

  switch (option)
  {
    case 1:
      a = add(x,y);
      printf("Sum = %f\n",a);
      break;
    case 2:
      s = subtract(x,y);
      printf("Difference = %f\n",s);
      break;
    case 3:
      m = multiply(x,y);
      printf("Product = %f\n",m);
      break;
    case 4:
      d = divide(x,y);
      printf("Ratio = %f\n",d);
      break;
    case 5:
      g = gcd((int)x,(int)y);
      printf("GCD = %d\n",g);
      break;
    case 6:
      printf("Quitting!!!!!\n");
      break;
  }

  if(option == 6)
  {break;}
  }
  return 0;
}