YeXiaoRain

is_ONE = (v)=>{
  let ret = 0;
  for(let i=1;i<=v;i++){
    // find divisor i
    if(!(v%i)){
      let mu = 1;
      // find prime factor of i
      for(let j=2;j <= i;j++){
        if(i%j)continue;
        // check if j is prime