summOfAllArguments(...a) {
    let sum = 0;
    for (let i in arguments) {
      if (arguments[i] instanceof Array){
        for(let q in arguments[i]){
          sum = +sum + arguments[i][q];
        }
      } else {
        sum = +sum + arguments[i];
      }
    }
    return sum;
  }
  let a = 1;
  let b = 2
  let c = 3;
  var arr = [1, 2, 3, 4, 5, 6, 7];
  this.summOfAllArguments(arr,a,b,c);