text: function solve() {
  	
  	let buttons = document.getElementsByTagName('button');
  
  	let sections= document.getElementsByTagName('section');
  	let secondSection = sections[1];
  	let thirdSection = sections[2];
  
  	let firstButton = buttons[0];
  	firstButton.addEventListener('click', function(){
  		secondSection.style.display="block";
  	});
  
  	let secondButton = buttons[2];
  	secondButton.addEventListener('click', function(){
  
  		if (secondSection.style.display==='none') {
  			
  		}
  		else{
  			thirdSection.style.display="block";
  		}
  	});
  }