/in/foo.cc: In function 'bool permutation(int)':
/in/foo.cc:38:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:42:5: warning: iteration 24 invokes undefined behavior [-Waggressive-loop-optimizations]
 k[i]=i;
 ~~~~^~
/in/foo.cc:41:16: note: within this loop
 for(R int i=1;i<=25;i++)
               ~^~~~