View Compilation Error

0_0_35133913_18149.cpp: In function 'int main()':
0_0_35133913_18149.cpp:47:7: error: 'f' was not declared in this scope
   mst(f,0);
       ^
0_0_35133913_18149.cpp:11:27: note: in definition of macro 'mst'
 #define mst(x, a) memset( x,a,sizeof(x) )
                           ^