diff --git a/main.py b/main.py
index 59325b9..b2bdcf3 100644
--- a/main.py
+++ b/main.py
@@ -9,31 +9,49 @@
 def add(x, y):
     """Add two integers."""
     # your code here
-    return
+    return x + y
 
 
 def multiply(x, y):
     """Multiply x with y using the add() function above."""
     # your code here
-    return
+    res = 0
+    for i in range(abs(y)):
+        res = add(res, abs(x))
+    if x < 0 < y or y < 0 < x:
+        return -res
+    return res
 
 
 def power(x, n):
     """Raise x to power n, where n >= 0, using the functions above."""
     # your code here
-    return
+    res = 1
+    for i in range(n):
+        res = multiply(res, x)
+    return res
 
 
 def factorial(x):
     """Compute the factorial of x, where x > 0, using the functions above."""
     # your code here
-    return
+    res = 1
+    for i in range(x, 0, -1):
+        res = multiply(res, i)
+    return res
 
 
 def fibonacci(n):
     """Compute the nth term of fibonacci sequence using the functions above."""
     # your code here
-    return
+    res = []
+    for i in range(n + 1):
+        if i < 2:
+            res.append(i)
+        else:
+            res.append(add(res[-2], res[-1]))
+    print(res)
+    return res[-1]
 
 
 if __name__ == '__main__':