Double free

#include <stdio.h>
#include <malloc.h>
int main(){

char *a = (char*) malloc(10);
char *b = (char*) malloc(10);
char *c = (char*) malloc(10);

printf("a is at memory %p \n",a);
printf("b is at memory %p \n",b);
printf("c is at memory %p \n",c);

free(a);
printf("Freeing a \n");


free(b);
printf("Freeing b  \n ");

free(c);
printf("Freeing c \n");
free(c);
printf("Freeing c twice \n");


return 0;

}