diff --git a/homework/2/11.py b/homework/2/11.py
new file mode 100644
index 0000000..15399ee
--- /dev/null
+++ b/homework/2/11.py
@@ -0,0 +1,6 @@
+x = []
+ans = 0
+for i in range(4):
+    x.append(list(map(float, input().split())))
+    ans += x[i][i] + x[i][3-i]
+print(ans)
diff --git a/homework/2/12.py b/homework/2/12.py
new file mode 100644
index 0000000..5aa47d4
--- /dev/null
+++ b/homework/2/12.py
@@ -0,0 +1,15 @@
+from math import *
+
+
+def zs(n):  # 朴素质数判断
+    if (n == 1):
+        return False
+    for i in range(2, floor(sqrt(n))+1):
+        if (n % i == 0):
+            return False
+    return True
+
+
+for i in range(1, 99):
+    if (zs(i) and zs(i+2)):
+        print(i, i+2)
diff --git a/homework/2/13.py b/homework/2/13.py
new file mode 100644
index 0000000..c1e37d4
--- /dev/null
+++ b/homework/2/13.py
@@ -0,0 +1,10 @@
+from math import *
+
+n, a = map(int, input().split())
+
+ans = 0
+
+for i in range(n):
+    ans += a*pow(10, i)*(n-i)
+
+print(floor(ans))
diff --git a/homework/2/14.py b/homework/2/14.py
new file mode 100644
index 0000000..53569be
--- /dev/null
+++ b/homework/2/14.py
@@ -0,0 +1,8 @@
+ans = 0
+a = 2
+b = 1
+for i in range(20):
+    ans += a/b
+    a = a+b
+    b = a-b
+print(round(ans, 2))
diff --git a/homework/2/15.py b/homework/2/15.py
new file mode 100644
index 0000000..67718af
--- /dev/null
+++ b/homework/2/15.py
@@ -0,0 +1,17 @@
+from math import *
+
+def zs(n):  # 朴素质数判断
+    if (n == 1):
+        return False
+    for i in range(2, floor(sqrt(n))+1):
+        if (n % i == 0):
+            return False
+    return True
+
+s = []
+
+for i in range(2,1000):
+    if(zs(i)):
+        s.append(i)
+
+print(s)
\ No newline at end of file
diff --git a/homework/2/16.py b/homework/2/16.py
new file mode 100644
index 0000000..7f81fd5
--- /dev/null
+++ b/homework/2/16.py
@@ -0,0 +1,6 @@
+x = list(map(int, input().split()))
+y = list(map(int, input().split()))
+s = x+y
+s.sort()
+for i in range(len(s)):
+    print(s[i], end=" ")
diff --git a/homework/2/17.py b/homework/2/17.py
new file mode 100644
index 0000000..b3d6b14
--- /dev/null
+++ b/homework/2/17.py
@@ -0,0 +1,8 @@
+n= int (input())
+x= []
+for i in range(n):
+    x.append(input().split()[0])
+s= input()
+for i in range(n):
+    if(s==x[i]):
+        print(i,end=" ")
\ No newline at end of file
diff --git a/homework/2/18.py b/homework/2/18.py
new file mode 100644
index 0000000..6bccbb4
--- /dev/null
+++ b/homework/2/18.py
@@ -0,0 +1,21 @@
+from math import *
+
+
+def S(a, b, c):
+    p = (a+b+c)/2
+    ans = (p*(p-a)*(p-b)*(p-c))**0.5
+    return round(ans, 2)
+
+
+def dis(a, b):
+    return sqrt((a[0]-b[0])**2+(a[1]-b[1])**2)
+
+
+s = []
+for i in range(3):
+    s.append(list(map(float, input().split())))
+
+a = dis(s[0], s[1])
+b = dis(s[1], s[2])
+c = dis(s[2], s[0])
+print("{:.2f}".format(S(a, b, c)))