const fs = require('fs/promises');

const tailVisited = {'0-0': true};

let hx = 0;
let hy = 0;
let tx = 0;
let ty = 0;

let lastHead = [0,0];

const moveRope = (direction) =>  {
  console.log("Moving ", direction);
  lastHead = [hx, hy];
  switch (direction) {
    case "R":
      hx += 1;
      break;
    case "L":
      hx -= 1;
      break;
    case "U":
      hy -= 1;
      break;
    case "D":
      hy += 1;
      break;
  }

  if(Math.max(Math.abs(hx - tx), Math.abs(hy - ty)) > 1) {
    [tx, ty ] = lastHead;
    console.log("Moving Tail to: ", tx, ", ", ty);
    tailVisited[`${tx}-${ty}`] = true;
  }
}

const printGraph = () => {
  console.log("\n\n");
  for(let y = -15; y <= 15; y++) {
    const row = ["·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·", "·"].map((spot, i) => {
        const x = i - 15;
        let ch = "·";
        if(!(y % 5) && !(x % 5)) {
          ch = "▪";
        }
        if(y === 0 && x === 0) {
          ch = "0";
        }
        if(y === ty && x === tx) {
          ch = "T";
        }
        if(y === hy && x === hx) {
          ch = "H";
        }
        return ch;
      });
    console.log(row.join(""));
  }
  console.log("\n\n");
};

(async () => {
  const input = await fs.readFile("./input.txt", 'utf8');

  const lines = input.split("\n").map(t => t.split(" "));

  //printGraph();
  for (const [direction, times] of lines) {
    for(let i = 0; i < times; ++i) {
      moveRope(direction);
      //printGraph();
    }
  }

  console.log(Object.values(tailVisited).length);
})();