.container {
 margin-bottom: 15px;
  }
.item {
  width: 50px;
  height: 50px;
  background: yellow;
  border:1px solid red;
  margin:0px;


}
.item1 {
   width: 450px;
  height: 50px;
  background:red;
   margin:0px;
}
.item2 {
   width: 450px;
  height: 50px;
  background: white;
}

.item3 {
   width: 450px;
  height: 50px;
  background: black;
}


.arrow-right {
  width: 0;
  height: 0;
  top: 0;
  border-top: 90px solid transparent;
    border-bottom: 90px solid transparent;

    border-left: 130px solid green;
    position: absolute;
  }