Some small problems in C

The first assignment of this course asked me to write some string manipulation functions without using any string library. I got stuck in the function 'mystrcpy'.

I typed following.

/*
* mystrcpy() copies the string pointed to by src (including the terminating character '\0') to the array pointed to by dst.
* Returns: a pointer to the destination string dst.
*/
char *mystrcpy (char *dst, const char *src)
{
　　/* Complete the body of the function */

　　int i;
　　while(src[i]!='\0'){
　　　　dst[i]=src[i];
　　　　i++;
　　}
　　dst[i]='\0';
　　return dst;
}

But terminal showed 'segementation fault'. I'm still thinking about this one.