题解 | #字符个数统计# new Set()

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
    while(str = await readline()){
        let arr = Array.from(new Set(str.split('')))
        console.log(arr.length)
    }
}()