div.imagenes{
  display: flex;
  justify-content: center;
  align-items: center;
  width: 300px;
  height: 200px;
  background-color:blue;
}
  div.ex1 {
  width:600px;
  margin: auto;
  justify-content: center;
  border: 3px solid #3358FF;
}

#contenedor input {
    display: block;
}