Как растянуть блок на всю высоту родителя?

.container { 
  width: 1024px; 
  height: auto; 
  margin: 0 auto; 
  display: flex; 
  justify-content: space-around; 
} 
 
.box-container { 
  width: 30%; 
  height: auto; 
  border: 2px solid gray; 
  display: flex;/* Раз */ 
  flex-direction: column;/*Два*/ 
} 
 
.box-header { 
  width: 100%; 
  height: 30px; 
  display: flex; 
  justify-content: space-around; 
  align-items: center; 
  font-size: 22px; 
  border-bottom: 1px solid lightgray; 
  background: rgb(230, 255, 230); 
} 
 
.box-main { 
  padding: 10px; 
  flex: 1 0 auto;/*Три*/ 
  background: rgb(255, 255, 230); 
} 
 
.box-footer { 
  width: 100%; 
  height: 30px; 
  display: flex; 
  justify-content: space-around; 
  align-items: center; 
  font-size: 22px; 
  border-top: 1px solid lightgray; 
  background: rgb(230, 247, 255); 
}

<div class="container"> 
 
  <div class="box-container"> 
    <div class="box-header">This is static HEADER</div> 
    <div class="box-main"><b>This is main content with dynamic char. </b> Lorem ipsum dolor sit amet, consectetur adipisicing elit. Dolorem aliquid autem alias iste error quasi porro vitae. 
    </div> 
    <div class="box-footer">This is static FOOTER</div> 
  </div> 
 
  <div class="box-container"> 
    <div class="box-header">This is static HEADER</div> 
    <div class="box-main"><b>This is main content with dynamic char. </b> Lorem ipsum dolor sit amet, consectetur adipisicing elit. Eius saepe ratione, expedita commodi, explicabo harum laborum quos quam dolorem fugit perferendis rerum magni ducimus itaque quis officia tenetur 
      cum. Doloremque magni ad illo libero minima maiores cumque, eius expedita quibusdam vero, ea dolore aliquid fuga porro sapiente explicabo molestiae. Et? 
    </div> 
    <div class="box-footer">This is static FOOTER</div> 
  </div> 
 
  <div class="box-container"> 
    <div class="box-header">This is static HEADER</div> 
    <div class="box-main"><b>This is main content with dynamic char. </b> Lorem ipsum dolor sit amet, consectetur adipisicing elit. Soluta veritatis vel, perspiciatis sequi dolores dicta debitis, earum dolore placeat repudiandae illo aspernatur eum illum provident culpa iusto 
      ducimus maxime odit. 
    </div> 
    <div class="box-footer">This is static FOOTER</div> 
  </div> 
 
</div>