added old solutions

py/3.py

@@ -0,0 +1,11 @@
+from sympy.ntheory import isprime
+import math
+
+def primefactor(x):
+    res = 0
+    for i in range(2,math.ceil(math.sqrt(x))):
+        if(not isprime(i) or x%i != 0): continue
+        res = i
+    return res
+
+print(primefactor(600851475143))