CrookedDigits

let input = [
    '1020340567.89',
];

let print = this.print || console.log;
let gets = this.gets || ((arr, index) => () => arr[index++])(input, 0);

let N = gets();

function summing(number){
let sum = 0;
number = number.toString().replace('.', '').replace('-', '');
do {
    sum += number%10;
    number = Math.floor(number/10);
}
while (number);
return sum;
}

let newN = summing(N);
while (newN > 9) {
    newN = summing(newN);
}

print(newN);