const fs = require('fs');

const input = fs.readFileSync(__dirname + '/input.txt', 'utf8');

let safe = 0;

function checkSequence(seq: Array<number>): boolean {
    let pointer = 0;
    let prev = seq[pointer];
    pointer++;
    let inc = seq[pointer] > prev;
    while (pointer < seq.length) {
        const next = seq[pointer];
        pointer++;
        if (inc ? next < prev : next > prev) {
            return false;
        }
        const diff = Math.abs(next - prev);
        if (diff <= 0 || diff > 3) {
            return false;
        }
        prev = next;
    }
    return true;
}

input.split("\n")
    .forEach((s: string) => {
        if (s.match('^\s*$')) {
            return;
        }
        const seq = s.split(' ').map((n) => parseInt(n));
        const isSafe = checkSequence(seq);
        if (!isSafe) {
            // Part 2
            for (let i = 0; i < seq.length; i++) {
                if (checkSequence([...seq.slice(0, i), ...seq.slice(i + 1)])) {
                    safe++;
                    return;
                }
            }
            // End part 2
            return;
        }
        safe++;
    });

console.log(safe);