Remove Spaces, Blanks from a String

/*
Write a program in C for 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;
}