@Danu: This is MetaPost, version 1.803 (MiKTeX 2.9 64-bit) 16 DEC 2014 13:46
**diagram
(mpost.mp (D:/Program Files (x86)/MiKTeX/metapost/base/plain.mp
Preloading the plain mem file, version 1.004) )
(C:/Users/***/2nd derivative/diagram.mp
(D:/Program Files (x86)/MiKTeX/metapost/feynmf/feynmp.mp) [1] )
Here is how much of MetaPost's memory you used:
301 strings using 4436 characters
1534584 bytes of node memory
922 symbolic tokens
14i,77n,28p,105b,3f stack positions out of 16i,96n,32p,200b,4f
1 output file written: diagram.1