/in/foo.cc: In function 'int main()':
/in/foo.cc:6:31: error: 'a' was not declared in this scope
  for(float i=0.0;i<n;i++)cin>>a[i];
                               ^
/in/foo.cc:8:31: error: 'a' was not declared in this scope
  for(float i=0.0;i<n;i++)sum+=a[i];
                               ^