function solve(arr) {
    let nums = arr[0].split(' ').map(x => Number(x));
    // 1 answer for the empty set
    let ans = 1;
    // nums.length answers for picking each element by itself
    if (nums.length >= 1) {
        ans += nums.length;
    }

    // calculate all arithmetic progressions made by picking 2 out of N, 3 out of N... N out of N
    // all 2 out of N progressions are always valid and can technically be extracted into a separate nChooseK calculation
    // but with progressions of 3 or more elements, we have to check if they are actually valid arithmetic progressions
    // i.e. 10 20 30 is but 10 20 45 is not 
    if (nums.length > 1) {
        for (let i = 2; i <= nums.length; i++) {
            for (let startIndex = 0; startIndex < nums.length - (i - 1); startIndex++) {
                recursivelyFindProgressions(i, startIndex, nums, 1, undefined);  
            }
        }
    }

    console.log(ans);

    function recursivelyFindProgressions(length, curIndex, nums, curLength, step) {
        for (let j = curIndex + 1; j < nums.length; j++) {
            let num = nums[j];
            let lastNum = nums[curIndex];
            if(curLength == 1) {
                step = num - lastNum;
            }

            if (step === (num - lastNum)) {
                if(curLength + 1 === length) {
                    ans++;
                } else {
                    recursivelyFindProgressions(length, j, nums, curLength + 1, step);
                }
            } 
        }
    }

}