Tip at Mars

MarsCurrency.js

function giveTip(currencyFirst, currencySecond, sum){
  let arr = [];
  arr[0] = 0;
  for(let i = 1; i <= sum; i++){
    let minA, minB;
    if( i < currencyFirst){
      minA = currencyFirst - i;
    }else{
       minA = arr[i - currencyFirst];
    }
    if( i < currencySecond){
      minB = currencySecond - i;
    } else {
      minB = arr [i - currencySecond]
    }
    arr[i] = Math.min(minA, minB);
  }
  return arr[sum];
}