#include <vector>
#include <iostream>

using namespace std;

int main( )
{
   vector<bool> shots( 5 ); // true if pet has shot

   // give shots to two pets
   shots[1] = true;
   shots[4].flip();


   // delete the first element because that pet was adopted
   shots.erase( shots.begin() );


   // flip bits to show pets needing shots
   shots.flip();

}
