diff --git a/fft.py b/fft.py
index f5633a8..ba54518 100644
--- a/fft.py
+++ b/fft.py
@@ -22,14 +22,17 @@ def fft(f):
         Fp = fft( fp )
         Fm.extend( Fp )
 
-    Fout=[0]*n
-    for k in range(n):
-        km = (k%m)
-        val = Fm[ km ]
-        for q in range(1,p):
-            t = e ** ( j*2*pi*k*q/n )
-            val += Fm[ q*m + km ] * t
-        Fout[k] = val
+    Fout = [ 0 ] * n
+    for u in range(m):
+        scratch = Fm[u::m] # u to end in strides of m
+        for q1 in range(p):
+            k = q1*m + u  # indices to Fout above that became scratch
+            val = Fm[ u ]
+            for q in range(1,p):
+                t = e ** ( j*2*pi*k*q/n )
+                #Fout[ k ] += scratch[q] * t
+                val += Fm[ q*m + u ] * t
+            Fout[ k ] = val
 
     return Fout