Change div position

.container {
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  -webkit-box-orient: vertical;
  -moz-box-orient: vertical;
  -webkit-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
  /* optional */
  -webkit-box-align: start;
  -moz-box-align: start;
  -ms-flex-align: start;
  -webkit-align-items: flex-start;
  align-items: flex-start;
}
  
.container .first_div {
  -webkit-box-ordinal-group: 2;
  -moz-box-ordinal-group: 2;
  -ms-flex-order: 2;
  -webkit-order: 2;
  order: 2;
}
  
.container .second_div {
  -webkit-box-ordinal-group: 1;
  -moz-box-ordinal-group: 1;
  -ms-flex-order: 1;
  -webkit-order: 1;
  order: 1;
}