/in/foo.cc: In function 'int main()':
/in/foo.cc:73:19: error: 'ia' was not declared in this scope
  for(int i=1;i<=n;ia++) 
                   ^~
/in/foo.cc:73:19: note: suggested alternative: 'i'
  for(int i=1;i<=n;ia++) 
                   ^~
                   i