diff --git a/library/generator.py b/library/generator.py
new file mode 100644
index 0000000..ea66ed5
--- /dev/null
+++ b/library/generator.py
@@ -0,0 +1,11 @@
+import random
+C = input()
+
+if C==1:
+  print 1
+elif C==2:
+  print 2
+elif C==3 or C==4:
+  print random.randint(3, 100)
+else:
+  print random.randint(2**(C**3-1), 2**(C**3))
diff --git a/library/grader.py b/library/grader.py
new file mode 100644
index 0000000..b98e56c
--- /dev/null
+++ b/library/grader.py
@@ -0,0 +1,39 @@
+x = input() + 1
+
+mat = [[0,0,1,0],[0,1,0,1],[1,0,2,0],[0,2,0,1]]
+mod = 10**9+7
+
+def egcd(a, b):
+    if a == 0:
+        return (b, 0, 1)
+    else:
+        g, y, x = egcd(b % a, a)
+        return (g, x - (b // a) * y, y)
+
+def modinv(a, m):
+    g, x, y = egcd(a, m)
+    if g != 1:
+        raise Exception('modular inverse does not exist')
+    else:
+        return x % m
+
+def matmult(mtx_a, mtx_b, mod):
+    tpos_b = zip( *mtx_b)
+    rtn = [[ sum( ea*eb for ea,eb in zip(a,b))%mod for b in tpos_b] for a in mtx_a]
+    return rtn
+
+def trace(A):
+    return sum(A[j][j] for j in range(len(A)))
+
+def matpow(A, p):
+    ret = A
+    for bit in bin(p)[3:]:
+        ret = matmult(ret, ret, mod)
+        if bit=='1':
+            ret = matmult(ret, A, mod)
+    return ret
+
+inv4 = modinv(4, mod)
+ans = trace(matpow(mat, x))%mod
+ans = (ans * inv4)% mod
+print ans
diff --git a/library2/description.md b/library2/description.md
index 9e733f0..449651a 100644
--- a/library2/description.md
+++ b/library2/description.md
@@ -28,3 +28,7 @@ Output:
 ```
 1
 ```
+
+Explanation: 
+
+If you understand the word 'ok', you can understand the word 'blah'. If you understand 'ok' and 'blah', you can understand 'iz'. 'iz', and 'ok' lets you understand 'yiq'. 'yiq', 'iz', and 'blah' let you understand 'arggiq'.