#include <stdio.h>

int main()  {
    struct st   {
        int i;
        struct st *j;
    }t1,t2;

    t1.i=123;
    t2.i=456;

    t1.j=&t2;
    t2.j=&t1;

    printf("%d\n%d\n", t2.j->i, t1.j->i);
}