题解 | #字符个数统计#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void async function () {
    while(line = await readline()){
      let nums = line.split("");

      let resSet = new Set(nums);
      let res = [...resSet]
      console.log(res.length);
    }
}()