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)
}
}()