Problem:
Score : 100 points

Problem Statement

We have five variables x_1, x_2, x_3, x_4, and x_5.

The variable x_i was initially assigned a value of i.

Snuke chose one of these variables and assigned it 0.

You are given the values of the five variables after this assignment.

Find out which variable Snuke assigned 0.

Constraints

The values of x_1, x_2, x_3, x_4, and x_5 given as input are a possible outcome of the assignment by Snuke.

Input

Input is given from Standard Input in the following format:

x_1 x_2 x_3 x_4 x_5

Output

If the variable Snuke assigned 0 was x_i, print the integer i.

Sample Input 1

0 2 3 4 5

Sample Output 1

1

In this case, Snuke assigned 0 to x_1, so we should print 1.

Sample Input 2

1 2 0 4 5

Sample Output 2

3

Solution in Go (1.14.1) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
	"strings"

	"flag"
	"runtime"
	"runtime/pprof"
)

var magic = 1000000007

var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
var memprofile = flag.String("memprofile", "", "write mem profile to file")

func solve() {
	io := NewIo()
	defer io.Flush()

	// PARSE HELPER SESSION

	// STR := io.Next()
	// Log("string", STR)

	// F := io.NextFloat()
	// Log("float", F)

	// parsing int array
	N := 5
	var A [200000]int
	for i := 0 ; i < N; i++ {
		A[i] = io.NextInt()
		if A[i] == 0 {
			fmt.Printf("%v\n", i+1)
			os.Exit(0)
		}
	}
	Logf("A %v\n", A[0:10])
	// sort.Sort(sort.Reverse(sort.IntSlice(A[:])))
	// sort.Sort(sort.IntSlice(A[:]))

	// parsing string as byte array
	// var s [10000]byte
	// var si [10000]int
	// str := io.Next()
	// for i := 0; i < len(str); i++ {
	// 	s[i] = str[i]
	//  // "0" = 48, "A" = 65, "a" = 97
	//  si[i] = int(str[i]) - 48
	// }
	// Log("byte array", s[0:10])

	// OUTPUT GENERATION PART
	// ans := 0
	// fmt.Printf("%v\n", ans)

	// if ans > 0 {
	//   fmt.Printf("Yes\n")
	// } else {
	//   fmt.Printf("No\n")
	// }

	// BFS/DFS PART
	// visited := []int{}
	// bfs/dfs(1, neighbor, func(node int) {
	// 	visited = append(visited, node)
	// })
	// fmt.Println(visited)

	// DFS 2
	// var dp [2000000]int
	// nei := make(map[int][]int)
	// nei[0] = []int{1, 2}
	// nei[1] = []int{0}
	// nei[2] = []int{0, 3}
	// nei[3] = []int{2}
	// dfs2(0, nei, func(n, p int) {
	// 	Logf("%v -> %v\n", p, n)
	// 	dp[n] = p
	// }, func(n, p int) {
	// 	Logf("%v -> %v\n", n, p)
	// })
	// Logf("%v\n", dp[0:5])

	// COMBINATION
	// fmt.Printf("%d %d %d\n", N, M, intMax(N, M))
	// fmt.Printf("Lucas %d %d\n", combMod(N, M, 13), combination(N, M))
}

func main() {
	flag.Parse()
	if *cpuprofile != "" {
		f, err := os.Create(*cpuprofile)
		if err != nil {
			Logf("%v\n", err)
			os.Exit(1)
		}
		pprof.StartCPUProfile(f)
		defer pprof.StopCPUProfile()
	}

	solve()

	if *memprofile != "" {
		f, err := os.Create(*memprofile)
		if err != nil {
			Logf("could not create memory profile: ", err)
			os.Exit(1)
		}
		defer f.Close() // error handling omitted for example
		runtime.GC() // get up-to-date statistics
		if err := pprof.WriteHeapProfile(f); err != nil {
			Logf("could not write memory profile: ", err)
			os.Exit(1)
		}
	}
}

// Libraries

// Io helps parsing inputs from standard input for programming contest.
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

// NewIo generates Io instance.
func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

// Flush flushes buffer. Don't forget to do this when you call Io.Printf/Io.PrintLn for final output.
func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

// NextLine parses line as string.
func (io *Io) NextLine() string {
	var buffer []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buffer = append(buffer, line...)
		if !isPrefix {
			break
		}
	}
	return string(buffer)
}

// Next parse next word as string.
func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	r := io.tokens[io.nextToken]
	io.nextToken++
	return r
}

// NextInt parse next word as Int.
func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

// NextFloat parses next word as float64.
func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

// PrintLn does buffer write with linefeed.
func (io *Io) PrintLn(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

// Printf does formatted buffer write.
func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

// PrintIntLn prints Int array in a single line.
func (io *Io) PrintIntLn(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.PrintLn(b...)
}

// PrintStringLn prints string array in a single line.
func (io *Io) PrintStringLn(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.PrintLn(b...)
}

// Log print single value to standard output (contest server ignores this so you don't have to remove when finishing)
func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

// Logf print formatted output to standard output (contest server ignores this so you don't have to remove when finishing)
func Logf(format string, a ...interface{}) {
	fmt.Fprintf(os.Stderr, format, a...)
}

func intMin(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func intMax(a, b int) int {
	if a > b {
		return a
	}
	return b
}

// direct calculation of combination
// n, m should be "small"
func combination(n, m int) int {
	if m > n {
		return 0
	} else if m == n || m == 0 {
		return 1
	} else {
		res := 1
		for i := 0; i < m; i++ {
			res *= (n - i)
		}
		for i := 1; i <= m; i++ {
			res /= i
		}
		return res
	}
}

// caluclate combination modulo based on Lucas theorem
func lucas(n, m, p int) int {
	ntemp := n
	mtemp := m
	res := 1
	for i := 0; i < 100; i++ {
		// fmt.Printf("ntemp: %d\n", ntemp)
		nreminder := ntemp % p
		ntemp = ntemp / p
		mreminder := mtemp % p
		mtemp = mtemp / p
		res = res * (combination(nreminder, mreminder) % p)
		if ntemp == 0 {
			break
		}
	}
	return res % p
}

func combMod(n, m, p int) int {
	return lucas(n, m, p)
}

func bfs(start int, nodes map[int][]int, fn func(int)) {
	frontier := []int{start}
	visited := map[int]bool{}

	for 0 < len(frontier) {
		next := []int{}
		for _, node := range frontier {
			visited[node] = true
			fn(node)
			for _, n := range bfsFrontier(node, nodes, visited) {
				next = append(next, n)
			}
		}
		frontier = next
	}
}

func bfsFrontier(node int, nodes map[int][]int, visited map[int]bool) []int {
	next := []int{}
	iter := func(n int) bool { _, ok := visited[n]; return !ok }
	for _, n := range nodes[node] {
		if iter(n) {
			next = append(next, n)
		}
	}
	return next
}

func dfs(node int, nodes map[int][]int, fn func(int)) {
	dfsRecur(node, nodes, map[int]bool{}, fn)
}

func dfsRecur(node int, nodes map[int][]int, v map[int]bool, fn func(int)) {
	v[node] = true
	fn(node)
	for _, n := range nodes[node] {
		if _, ok := v[n]; !ok {
			dfsRecur(n, nodes, v, fn)
		}
	}
}

// handles 2 function, one is before entering child tree, and another is
// after entering child tree.
func dfs2(node int, nodes map[int][]int, fn1, fn2 func(int, int)) {
	dfs2Recur(node, -1, nodes, map[int]bool{}, fn1, fn2)
}

func dfs2Recur(node, parent int, nodes map[int][]int, v map[int]bool, fn1, fn2 func(int, int)) {
	v[node] = true
	if fn1 != nil {
		fn1(node, parent)
	}
	for _, n := range nodes[node] {
		if _, ok := v[n]; !ok {
			dfs2Recur(n, node, nodes, v, fn1, fn2)
		}
	}
	if fn2 != nil {
		fn2(node, parent)
	}
}

// Stack data structure
type Stack struct {
	top  *Element
	size int
}

// Element is a struct for stack element
type Element struct {
	value interface{}
	next  *Element
}

// Len returns stack height
func (s *Stack) Len() int {
	return s.size
}

// Push put a element on the stack.
func (s *Stack) Push(value interface{}) {
	s.top = &Element{value, s.top}
	s.size++
}

// Pop picks out the last element from the stack.
func (s *Stack) Pop() (value interface{}) {
	if s.size > 0 {
		value, s.top = s.top.value, s.top.next
		s.size--
		return
	}
	return nil
}

// powerInt (use math.Pow() for float parameters)
func powerInt(n, p int) int {
	tmp := 1
	for i := 0; i < n; i++ {
		tmp *= p
	}
	return tmp
}

func findDivisors(n int, a *[]int) {
	if n == 1 {
		return
	}

	sqrt := int(math.Sqrt(float64(n)))
	for i := 2; i <= sqrt; i++ {
		if n%i == 0 {
			*a = append(*a, i)
			*a = append(*a, n/i)
		}
	}
	*a = append(*a, n)
}

func removeDuplicate(a []int) []int {
	m := make(map[int]bool)
	for i := 0; i < len(a); i++ {
		m[a[i]] = true
	}
	res := []int{}
	for i := range m {
		res = append(res, i)
	}
	return res
}

func abs(a int) int {
	if a > 0 {
		return a
	}
	return -a
}

// var gcdmap map[int](map[int]int)
// func gcd(a, b int) int {
// 	ina := a
// 	inb := b
// 	if _, ok := gcdmap[a]; !ok {
// 		gcdmap[a] = make(map[int]int)
// 	}
// 	if _, ok := gcdmap[ina][inb]; ok {
// 		return gcdmap[ina][inb]
// 	}
// 	for b != 0 {
// 		t := b
// 		b = a % b
// 		a = t
// 	}
// 	gcdmap[ina][inb] = a
// 	return a
// }

func gcd(a, b int) int {
	for a != 0 {
		a, b = b % a, a
	}
	return b
}

func power2mod(n, mod int) int {
	res, x := 1, 2
	for ; n > 0; n >>= 1 {
		if n&1 == 1 {
			res = res * x % mod
		}
		x = x * x % mod
	}
	return res
}

func power2(n int) int {
	return power2mod(n, magic)
}