diff --git a/optimizer/box-breaker.cpp b/optimizer/box-breaker.cpp
index 6a14c21..904e201 100644
--- a/optimizer/box-breaker.cpp
+++ b/optimizer/box-breaker.cpp
@@ -163,8 +163,8 @@ inline int solve(Maze q) {
 };	// namespace Solve
 
 const float initial_temperature = 10;
-const float initial_temperature_pv = 70;
-const float termperature_delta = .98;
+const float initial_temperature_pv = 60;
+const float termperature_delta = .97;
 const int population_limit = 30;
 
 struct Gene {
@@ -186,11 +186,14 @@ inline void expandAll(Maze q, std::vector<Gene> &res, float t = initial_temperat
 		for (int j : {0, 1}) {
 			for (int d : {-1, 1}) {
 				compiler_assume(q.poi[i][j] >= 0 && q.poi[i][j] < N);
-				int z = q.poi[i][j] + d;
-				if (0 <= z && z < N) {
-					q.poi[i][j] += d;
-					expand(q, res, t);
-					q.poi[i][j] -= d;
+				q.poi[i][j] += d;
+				if (0 <= q.poi[i][j] && q.poi[i][j] < N) {
+					bool flag = false;
+					for (int k = 0; k < POI_EXCEED; ++k)
+						flag |= (q.poi[i][0] == q.poi[k][0] && q.poi[i][1] == q.poi[k][1]);
+
+					if (!flag)
+						expand(q, res, t);
 				}
 			}
 		}