package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"time"
)

func main() {
	start := time.Now()
	partOne()
	duration := time.Since(start)
	fmt.Printf("p1: %s, p2: n/a\n", duration)
}

func partOne() {
	f, _ := os.Open("input")
	reader := bufio.NewReader(f)
	scanner := bufio.NewScanner(reader)

	scanner.Scan()
	doorPubKey, _ := strconv.Atoi(scanner.Text())
	scanner.Scan()
	cardPubKey, _ := strconv.Atoi(scanner.Text())

	subjectNumber := 7
	value := 1
	magicPrime := 20201227
	loopCount := 1
	doorLoopCount := 0
	cardLoopCount := 0
	for {
		value = (value * subjectNumber) % magicPrime
		if value == doorPubKey {
			doorLoopCount = loopCount
		}
		if value == cardPubKey {
			cardLoopCount = loopCount
		}
		loopCount = loopCount + 1
		if doorLoopCount != 0 && cardLoopCount != 0 {
			break
		}
	}

	value = 1
	subjectNumber = cardPubKey
	for i := 0; i < doorLoopCount; i = i + 1 {
		value = (value * subjectNumber) % magicPrime
	}
	fmt.Println(value)
}