text: function fibonacci(n) {
      let a = 0;
      let b = 1;
      let ac = 1;
      let sum = 0;
      for (let i = 0; i <= n; i++) {
          ac = a + b;
          b = a;
          a = ac;
          sum += ac;
          // console.log(ac);
      }
      if (n === 0) {
          sum = 1;
      }
      // sum = sum * 4;
      console.log(sum);
  }
  
  fibonacci(4);
  
  function perimeter(n) {
      const arr = [0, 1];
      for (let i = 0; i < n; i++) {
          arr.push(arr[arr.length - 1] + arr[arr.length - 2])
      }
      let sum = arr.reduce((acc, current) => acc + current);
      return 4 * sum;
  }
  
  // console.log(perimeter(0));