Add euler 9 problem

euler/.gitignore

@@ -4,4 +4,5 @@ problem03
 problem04
 problem05
 problem06
-problem07
+problem07
+problem09

euler/problem09.porth

@@ -0,0 +1,21 @@
+include "std.porth"
+
+macro sum 1000 end
+
+sum
+1 while over over >= do
+  1 while over over >= do
+    2dup over dup * over dup * +
+    rot rot
+    + sum swap -
+    if 2dup dup * = do
+      swap drop print
+      2dup swap print print
+      0 exit  // can be commented to test that it's the only one solution
+    else
+      2drop
+    end
+    1 +
+  end drop
+  1 +
+end 2drop

euler/problem09.txt

@@ -0,0 +1,11 @@
+:i argc 0
+:b stdin 0
+
+:i returncode 0
+:b stdout 12
+425
+375
+200
+
+:b stderr 0
+