stergerea unui subsir dintr-un sir

#include <iostream>
#include <string.h>
using namespace std;

int main()
{
    char a[100], b[100], *p ;
    cin>>a;
    cin>>b;
    p=strstr(a,b);
    int l=strlen(b);
    if(p==0)
        cout<<"Nu exista subsirul respectiv.";
    else
        do
        {
            strcpy(p, p+l);
            p=strstr(p, b);
        }while(p);
    cout<<a;
    return 0;
}