#include <stdio.h>

int main(void) {
   double x, y;

   printf("Enter two numbers: ");
   scanf("%lf%lf", &x, &y);
   printf("Average of %g and %g: %g\n", x, y, average(x, y));

   return 0;
}

double average(double a, double b) {
   return (a + b) / 2;
}