<?php

$instructions = explode("\n", file_get_contents('input.txt'));

$acc = 0;
$used_indexes = [];
$current_index = 0;

while (true) {
    if (in_array($current_index, $used_indexes, true)) {
        echo $acc;
        exit;
    }
    $used_indexes[] = $current_index;
    $current_op = $instructions[$current_index];
    [$command, $value] = explode(' ', $current_op);

    if ($command === 'nop') {
        $current_index++;
        continue;
    }

    $math_op = $value[0];
    $math_value = substr($value, 1);

    if ($command === 'acc') {
        if ($math_op === '+') {
            $acc += (int)$math_value;
        } else {
            $acc -= (int)$math_value;
        }
        $current_index++;
        continue;
    }

    if ($command === 'jmp') {
        if ($math_op === '+') {
            $current_index += (int)$math_value;
        } else {
            $current_index -= (int)$math_value;
        }
        continue;
    }
}