foo.cc: In function ‘int main()’:
foo.cc:10:13: error: ‘i’ was not declared in this scope
   10 |         for(i=0; i<=n-1; i++)
      |             ^
foo.cc:15:13: error: ‘i’ was not declared in this scope
   15 |         for(i=0; i<=n-1; i++)
      |             ^
foo.cc:14:13: warning: unused variable ‘a’ [-Wunused-variable]
   14 |         int a=1;
      |             ^