题解 | #字符个数统计#

const readline = require('readline')

var rl = readline.createInterface({
    input:process.stdin,
    output:process.stdout
})
var str = ''
rl.on('line',(line)=>{
    str = line
})
rl.on('close',()=>{
   var arr = str.split('')
   var s = new Set(arr.reverse())
   var arr2 = [...s]
   console.log(arr2.length)
})