diff --git a/layer.py b/layer.py
index 0e3e9bd..94235f2 100644
--- a/layer.py
+++ b/layer.py
@@ -6,6 +6,31 @@ import io
 #only scalar gradient
 #op must be tree. 그래프 구현할려면, 위상정렬해서 순회해야하기 때문에 그렇게 하지 않음.
 
+def broadcasting_be(a,b):
+    i = len(a)-1
+    j = len(b)-1
+    abroad = []
+    bbroad = []
+    while i >= 0 and j >= 0:
+        if a[i] == b[j]:
+            abroad.insert(0,1)
+            bbroad.insert(0,1)
+        elif a[i] == 1 or b[j] == 1:
+            abroad.insert(0,b[j])
+            bbroad.insert(0,a[i])
+        else:
+            raise ValueError
+        i -= 1
+        j -= 1
+    while i >= 0:
+        bbroad.insert(0,a[i])
+        i -= 1
+    while j >= 0:
+        abroad.insert(0,b[j])
+        j -= 1
+    return abroad, bbroad
+
+
 class NonExistVarableError(ValueError):
     pass
 
@@ -91,13 +116,15 @@ class AddOp(OpTree):
         return self.v
 
     def backprop(self,seed):
-        #borad_casted = self.a.shape != self.b.shape
-        #np.ones((1,b.shape[1]))
         #a + b
+        ashape, bshape = broadcasting_be(self.a.numpy().shape,self.b.numpy().shape)
+        aai = np.where(np.array(ashape) != 1)
+        bbi = np.where(np.array(bshape) != 1)
         if isinstance(self.a,OpTree):
-            self.a.backprop(seed)
+            self.a.backprop(np.sum(seed,axis=tuple(aai[0])))
         if isinstance(self.b,OpTree):
-            self.b.backprop(seed)
+            self.b.backprop(np.sum(seed,axis=tuple(bbi[0])))
+
 
 def addmul(a,b):
     return AddOp(a,b)
@@ -163,30 +190,3 @@ class Variable(OpTree):
         writer.write(f'{id(self)}["Variable{self.x.shape}"]\n')
     def backprop(self,seed):
         self.grad = seed
-
-
-"""
-input_var = Variable(np.array([[1],[2],[3]]))
-weight = Variable(np.array([[2,-1,1]]))
-v = relu(weight @ input_var)
-print(f"result : {v.numpy()}")
-v.backprop(np.ones(()))
-print(f"grad input : {input_var.grad}, w : {weight.grad}")
-"""
-
-#input_diff = Variable(np.array([[1.01],[2],[3]]))
-#v_diff = relu(weight @ input_diff)
-#print(f"diff 1 : {(np.sum(v_diff.numpy()) - v.numpy()) / 0.01}")
-
-#i -= grad * delta
-
-"""
-graph TD
-2284612545696["Variable(1, 3)"]
-2284612545696-->2284612624880[MatmulOp]
-2284612544496["Variable(3, 2)"]
-2284612544496-->2284612624880[MatmulOp]
-2284612624880-->2284612625072[FunctionReluOp]
-2284612625072-->2284612627856[MatmulOp]
-2284612627856-->Result
-"""
\ No newline at end of file
diff --git a/p2.py b/p2.py
index 62248b4..d745fd5 100644
--- a/p2.py
+++ b/p2.py
@@ -1,7 +1,7 @@
 from layer import *
 import numpy as np
 import pickle
-
+"""
 DIMENTION = 3
 VAR_RANGE = 1
 N = 10
@@ -18,15 +18,17 @@ y = or_weight @ input_x + or_bias
 error = gen.normal(0,SIGMA,size = (1,N))
 y += error
 print(y)
+"""
 
+input_var = Variable(np.array([[1,2,3],[1,5,0]]))
+weight = Variable(np.array([[2],[-1],[1]]))
+bias = Variable(np.array([1]))
+v = relu((input_var @ weight) + bias)
+#print(v.numpy())
+#print(v.numpy().shape, np.array([[1,1]]).shape)
+k = matmul(np.array([[1,1]]), v)
+print(make_mermaid_graph(k))
 
-input_var = Variable(np.array([[1],[2],[3]]))
-weight = Variable(np.array([[2,-1,1]]))
-bias = Variable(np.array([[1]]))
-v = ((weight @ input_var) + bias)
-
-print(make_mermaid_graph(v))
-
-print(f"result : {v.numpy()}")
-v.backprop(np.ones(()))
+print(f"result : {k.numpy()}")
+k.backprop(np.ones(()))
 print(f"grad input : {input_var.grad}, w : {weight.grad}, b : {bias.grad}")