remove spaces, blanks from a string

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define SPACE ' '
 
main()
{
   char string[100], *blank, *start;
   int length, c = 0, d = 0;
 
   printf("Enter a string\n");
   gets(string);
 
   length = strlen(string);
 
   blank = string;
 
   start = (char*)malloc(length+1);
 
   if ( start == NULL )
      exit(EXIT_FAILURE);
 
   while(*(blank+c))
   {
      if ( *(blank+c) == SPACE && *(blank+c+1) == SPACE )
      {}
      else
      {
         *(start+d) = *(blank+c);
  d++;
      }
      c++;
   }
   *(start+d)='\0';
 
   printf("%s\n", start);
 
   free(start);     
 
   return 0;
}