编辑代码

// 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 (async function () {
  const m = Number(await readline());
  const arrA = (await readline()).split(" ").map(Number);
  const n = Number(await readline());
  const arrB = (await readline()).split(" ").map(Number);
  let ans = 0;
  const map = new Map();
  for (let i = 0; i < m; i++) {
    map.set(arrA[i], map.get(arrA[i]) ? [...map.get(arrA[i]), i] : [i]);
  }
  for (let j = 0; j < n; j++) {
    if (map.has(arrB[j])) {
      ans += [...map.get(arrB[j])].length;
    }
  }
  console.log(ans);
  // for(const val )
})();