// 设置标准输入接口const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void (asyncfunction () {
const n = Number(await readline());
const arr = (await readline()).split("").map(Number);
let i = 0,
j = n - 1;
while (i < j) {
let a = arr[i];
let b = arr[j];
// if (// arr.includes((a - b) / 2) ||// arr.includes((b - a) / 2) ||// arr.includes(a - b * 2) ||// arr.includes(b - a * 2) ||// arr.includes(a + b * 2) ||// arr.includes(b + a * 2)// ) {// console.log(a, b);// }const hasA = arr.findIndex(
(val, idx) => val == (a - b) / 2 && idx !== i && idx !== j
);
const hasB = arr.findIndex(
(val, idx) => val == (b - a) / 2 && idx !== i && idx !== j
);
const hasC = arr.findIndex(
(val, idx) => val == a - b * 2 && idx !== i && idx !== j
);
const hasD = arr.findIndex(
(val, idx) => val == b - a * 2 && idx !== i && idx !== j
);
const hasE = arr.findIndex(
(val, idx) => val == a + b * 2 && idx !== i && idx !== j
);
const c = [hasA, hasB, hasC, hasD, hasE].filter((val) => val !== -1)[0];
if (a == b + 2 * arr[c]) returnconsole.log(a, b, arr[c]);
if (a == arr[c] + b * 2) returnconsole.log(a, arr[c], b);
if (b == a + 2 * arr[c]) returnconsole.log(b, a, arr[c]);
if (b == arr[c] + a * 2) returnconsole.log(b, arr[c], a);
if (arr[c] == a + b * 2) returnconsole.log(arr[c], a, b);
if (arr[c] == b + a * 2) returnconsole.log(arr[c], b, a);
j--;
}
console.log(0);
})();