diff --git a/source/solver.c b/source/solver.c
index e1edab2711e337873c9a8cad472c8e1808b785e2..01501c2ddcf7a98293f01e03b04f668466e544da 100644
--- a/source/solver.c
+++ b/source/solver.c
@@ -1,5 +1,5 @@
 /* solver.c */
-/* Last Change: 2018/08/27 (Mon) 23:01:56. */
+/* Last Change: 2018/08/27 (Mon) 23:42:09. */
 
 #define MAX_ATTEMPS 10000
 
@@ -19,6 +19,8 @@ int lines;
 int dx[6]={-1,0,0,1,0,0};
 int dy[6]={0,-1,0,0,1,0};
 int dz[6]={0,0,-1,0,0,1};
+int history[8*72*72];
+int searchorder[6]; //x+-,y+-,z+-
 //z,y,x
 
 void read(void){ //read problem
@@ -77,12 +79,14 @@ void read(void){ //read problem
 }
 
 int available(int z,int y, int x){ //return 1 when (nowx,nowy,nowz) can be connected to goal
-	int i,src=0,contd,isbranch;
-	int history[8*72*72],index=0;
+	int i,j,t,src=0,contd,isbranch;
+	int index=0;
 	int nowx=x,nowy=y,nowz=z;
-	int searchorder[6]; //x+-,y+-,z+-
 	/* for(i=0;i<6;i++) */
 	/* printf("%d %d %d\n",dx[i],dy[i],dz[i]); */
+	for(i=0;i<8*72*72;i++)
+		history[i]=-1;
+	index=0;
 	while(1){
 		/* printf("%d %d %d\n",nowx,nowy,nowz); */
 		if(nowx<0||nowy<0||nowz<0||nowx>=width||nowy>=height||nowz>=depth){
@@ -111,13 +115,17 @@ int available(int z,int y, int x){ //return 1 when (nowx,nowy,nowz) can be conne
 			avail[nowz][nowy][nowx]=0;
 			index--;
 			if(nowx-dx[history[index]]<0||nowy-dy[history[index]]<0||nowz-dx[history[index]]<0||nowx-dz[history[index]]>=width||nowy-dy[history[index]]>=height||nowz-dz[history[index]]>=depth){
+				index++;
 				/* printf("something wrong\n"); */
 			}else{
 				nowx-=dx[history[index]];
 				nowy-=dy[history[index]];
 				nowz-=dz[history[index]];
 				avail[nowz][nowy][nowx]=1;
-				printf("%d %d %d -\n",nowx,nowy,nowz);
+				/* printf("%d %d %d -%d %d\n",nowx,nowy,nowz,history[index],index); */
+				/* for(j=0;j<index;j++) */
+				/* 	printf("%d ",history[j]); */
+				/* printf("\n"); */
 				/* return 0;//goback */
 				continue;
 			}
@@ -154,7 +162,6 @@ int available(int z,int y, int x){ //return 1 when (nowx,nowy,nowz) can be conne
 			src++;
 		}else
 			searchorder[src]=5;
-		int j,t;
 		for(i=0;i<src;i++){
 			j=rand()%(src);
 			t=searchorder[i];
@@ -178,9 +185,11 @@ int available(int z,int y, int x){ //return 1 when (nowx,nowy,nowz) can be conne
 				nowy+=dy[searchorder[i]];
 				nowz+=dz[searchorder[i]];
 				/* printf("%d %d %d\n",dx[searchorder[i]],dy[searchorder[i]],dz[searchorder[i]]); */
-				printf("%d %d %d +\n",nowx,nowy,nowz);
 				history[index]=searchorder[i];
-				/* printf("%d\n",index); */
+				/* printf("%d %d %d +%d %d\n",nowx,nowy,nowz,searchorder[i],index+1); */
+				/* for(j=0;j<index;j++) */
+				/* 	printf("%d ",history[j]); */
+				/* printf("\n"); */
 				index++;
 			}
 		}
@@ -190,13 +199,17 @@ int available(int z,int y, int x){ //return 1 when (nowx,nowy,nowz) can be conne
 			avail[nowz][nowy][nowx]=0;
 			index--;
 			if(nowx-dx[history[index]]<0||nowy-dy[history[index]]<0||nowz-dx[history[index]]<0||nowx-dz[history[index]]>=width||nowy-dy[history[index]]>=height||nowz-dz[history[index]]>=depth){
+				index++;
 				/* printf("something wrong\n"); */
 			}else{
 				nowx-=dx[history[index]];
 				nowy-=dy[history[index]];
 				nowz-=dz[history[index]];
 				avail[nowz][nowy][nowx]=1;
-				printf("%d %d %d -\n",nowx,nowy,nowz);
+				/* printf("%d %d %d -%d %d\n",nowx,nowy,nowz,history[index],index); */
+				/* for(j=0;j<index;j++) */
+				/* 	printf("%d ",history[j]); */
+				/* printf("\n"); */
 				/* printf("%d %d %d\n",dx[history[index]],dy[history[index]],dz[history[index]]); */
 				continue;
 			}