/in/foo.cc: In function 'int Merge(int*, int, int*, int)':
/in/foo.cc:32:6: warning: variable 'i' set but not used [-Wunused-but-set-variable]
  int i; 
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:51:6: warning: unused variable 'n4' [-Wunused-variable]
  int n4=Merge(a1,n1,a2,n2);
      ^~
/in/foo.cc:52:6: warning: unused variable 'n5' [-Wunused-variable]
  int n5=Merge(a1,n1,a3,n3);
      ^~