JSFiddle - React, Tailwind, and code Playground

JavaScript

let input = [
  '5',
  '23',
  '54',
  '3',
  '12',
  '32',
 
];


let print = this.print || console.log;
let gets = this.gets || ((arr, index) => () => arr[index++])(input, 0);

let n = +gets();

let numbersArray = [];

for (let i = 0; i < n; i++ ) {
      numbersArray.push(+gets());
}

var largest = 0;
var secLar = 0;
var thirLar = 0;


      if (3 <= n <= 20 && -500 <= numbersArray <= 500) {
      
for (let i = 0; i < numbersArray.length; i++) {

      if (numbersArray[i] > largest) {
            var largest = numbersArray[i];
            
      }

      if (numbersArray[i] > secLar < largest ) {
            var secLar = numbersArray[i];
            
      }

      if (numbersArray[i] > thirLar < secLar && numbersArray[i] > thirLar < largest) {
            var thirLar = numbersArray[i];
      }

}

      }

alert(largest +', ' + secLar + ' and ' + thirLar );