text: function lettersChangeNumbers(input) {
      const isUpperCase = (symbol) => {
          return symbol === symbol.toUpperCase();
      };
  
      let words = input.split(' ')
          .filter((el) => el !== '');
      let totalSum = 0;
  
      for (let word of words) {
          let firstLetter = word[0];
          let lastLetter = word[word.length - 1];
          let number = Number(word.substring(1, word.length - 1));
          let firstAscii = firstLetter.toLowerCase().charCodeAt(0);
          let lastAscii = lastLetter.toLowerCase().charCodeAt(0);
  
          if (isUpperCase(firstLetter)) {
              totalSum += number / (firstAscii - 96);
          } else {
              totalSum += number * (firstAscii - 96);
          }
  
          if (isUpperCase(lastLetter)) {
              totalSum -= lastAscii - 96;
          } else {
              totalSum += lastAscii - 96;
          }
      }
  
      console.log(totalSum.toFixed(2));
  }
  
  lettersChangeNumbers('A12b s17G');