/in/foo.cc: In function 'int Mul(int, int, int*, int)':
/in/foo.cc:7:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(i=1;i<n;i++)
  ^~~
/in/foo.cc:14:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   return j;
   ^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:21:6: warning: unused variable 'na' [-Wunused-variable]
  int na=Mul(x,n,a,k);
      ^~