void lcs_LCS(obj, s1, s2)
    SV *obj
    AV * s1
    AV * s2

    PREINIT:
        struct CTX *ctx = (struct CTX *)SvIVX(SvRV(obj));

    PPCODE:
        int d, sn, i;
        struct varray *ses = varray_new(sizeof(struct diff_edit), NULL);
  
        IV n;
        IV m;
        n = av_top_index(s1);
        m = av_top_index(s2);

        d = diff(s1, 0, n+1, s2, 0, m+1, &_cmp_idx,  NULL, 0, ses, &sn, NULL);

 
  int x,y,j;
  x=y=0;

  XSprePUSH;

  for (i = 0; i < sn; i++) {
  	struct diff_edit *e = varray_get(ses, i);
  
  	switch (e->op) {
  		case DIFF_MATCH:
  		    //printf("MAT: ");
  			//printf("off %d len %d\n", e->off, e->len);
  		    for (j = 0; j < e->len; j++) {
  		      //printf("x %d y %d\n", x, y);
  		      
  		      AV *arr;
              arr = newAV();
              av_push(arr, newSViv(x));
              av_push(arr, newSViv(y));
              XPUSHs(sv_2mortal(newRV_noinc((SV *)arr)));
                    
  			  x++;
  			  y++;
  			}
  			break;
  		case DIFF_DELETE:
  			//printf("DEL: ");
  			//printf("off %d len %d\n", e->off, e->len);
  			for (j = 0; j < e->len; j++) {
  			  x++;
  			}
  			break;
  		case DIFF_INSERT:
  			//printf("INS: ");
  			//printf("off %d len %d\n", e->off, e->len);
  			for (j = 0; j < e->len; j++) {
  			  y++;
  			}
  			break;
  	}
  }

                
                
  varray_del(ses);