I want to write a program that erases all characters in string 1 that appear in string 2 , using pointers . 
This is what I did , but it did not work .

```
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
main()
{
    char ch1[100] , ch2[100] ;
    char *p1 , *p2;
    printf("first chaine ");
    gets(ch1);
    printf("sd chaine");
    gets(ch2);
    for(p1=ch1;p1<ch1+100;p1++)
    {
        for(p2=ch2;p2<ch2;p2++)
        {
            if(*p1==*p2)
            {
                strcpy(p1,p1+1);
            }
        }
    }
    puts(ch1);
    return 0 ;
}

```