3. 제로

const fs = require("fs");
const filePath = process.platform === "linux" ? "/dev/stdin" : "./input.txt";
let [k, ...nums] = fs.readFileSync(filePath).toString().trim().split("\n");
let sum = 0;

for (i = 0; i < nums.length; i++) {
  if (nums[i] == 0) {
    sum -= nums[i - 1];
    nums.splice(i - 1, 2);
    i -= 2;
  } else sum += +nums[i];
}

console.log(sum);

---

// 런타임 에러 (TypeError) 발생 코드
const fs = require("fs");
const filePath = process.platform === "linux" ? "/dev/stdin" : "./input.txt";
let [k, ...nums] = fs.readFileSync(filePath).toString().trim().split("\n");
let rightNums = [];

nums.forEach((ele) => {
  if (ele == 0) rightNums.pop();
  else rightNums.push(+ele);
});

console.log(rightNums.reduce((acc, cur) => acc + cur));