part1.ts

import * as fs from 'fs';
const input = fs.readFileSync('input', 'utf8').split('\n');

let x = 0;
let y = 0;
const points = [];
let perimeter = 0;
for (let i = 0; i < input.length; i++) {
	const line = input[i].split(' ');
	const direction = line[0];
	const steps = Number(line[1]);
	switch (direction) {
		case 'R':
			x += steps;
			break;
		case 'L':
			x -= steps;
			break;
		case 'U':
			y -= steps;
			break;
		case 'D':
			y += steps;
			break;
	}
	perimeter += steps;
	points.push([x, y]);
}

let result = 0;

for (let i = 0; i < points.length - 1; i++) {
	// Shoelace formula
	result += points[i][0] * points[i + 1][1] - points[i + 1][0] * points[i][1];
}
result += perimeter;

console.log(Math.floor(result / 2) + 1);