const rl = require("readline").createInterface({ input: process.stdin }); var iter = rl[Symbol.asyncIterator](); const readline = async () => (await iter.next()).value; void async function () { // Write your code here let arr = []; let len = await readline(); let obj = { push:(n)=>arr.push(n), pop:()=>arr.shift(), front:()=>arr[0] } for(let i =0;i<len;i++){ let sk = (await readline()).split(' '); let type = sk[0]; let value = sk[1]; type!=='push'? console.log(obj[type]()||'error'):obj[type](value) } }()