ACM - UVA - 465 - Overflow

#include <stdio.h>
#include <stdlib.h>

int main ()
{
 long double x, y;
 char a [10000], b [10000], c;

 while ( scanf ("%s %c %s", a, &c, b) == 3) {
  x = atof (a);
  y = atof (b);
  printf("%s %c %s\n", a, c, b);

  if ( x > 2147483647 )
   printf("first number too big\n");
  if ( y > 2147483647 )
   printf("second number too big\n");
  if ( c == '+' ) {
   x = x + y;
   if ( x > 2147483647 )
   printf("result too big\n");
  }
  else {
   x = x * y;
   if ( x > 2147483647 )
   printf("result too big\n");
  }
 }
 return 0;
}