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)

//go:generate echo "https://atcoder.jp/contests/abc170/tasks/abc170_a"
package main

import (
	"bufio"
	"fmt"
	"io"
	"math/big"
	"os"
	"strconv"
)

var sc = newScanner(os.Stdin)

func Solve(X []int) int {
	for i, x := range X {
		if x == 0 {
			return i + 1
		}
	}
	return -1
}

func main() {
	fmt.Println(Solve(sc.Ints(5)))
}

type scanner struct {
	*bufio.Scanner
}

func newScanner(r io.Reader) *scanner {
	s := bufio.NewScanner(r)
	s.Split(bufio.ScanWords)
	s.Buffer(nil, 100000000)
	return &scanner{s}
}

func (s *scanner) String() string {
	s.Scan()
	return s.Text()
}

func (s *scanner) Strings(l int) []string {
	if l == 0 {
		return []string{}
	}
	sl := make([]string, l, l)
	for i := range sl {
		sl[i] = s.String()
	}
	return sl
}

func (s *scanner) Int() int {
	n, _ := strconv.Atoi(s.String())
	return n
}

func (s *scanner) Ints(l int) []int {
	if l == 0 {
		return []int{}
	}
	sl := make([]int, l, l)
	for i := range sl {
		sl[i] = s.Int()
	}
	return sl
}

func (s *scanner) Float64() float64 {
	f, _ := strconv.ParseFloat(s.String(), 64)
	return f
}

func (s *scanner) Floats64(l int) []float64 {
	if l == 0 {
		return []float64{}
	}
	sl := make([]float64, l, l)
	for i := range sl {
		sl[i] = s.Float64()
	}
	return sl
}

func (s *scanner) BigInt() *big.Int {
	n, _ := strconv.ParseInt(s.String(), 10, 64)
	return big.NewInt(n)
}

func (s *scanner) BigInts(l int) []*big.Int {
	if l == 0 {
		return []*big.Int{}
	}
	sl := make([]*big.Int, l, l)
	for i := range sl {
		sl[i] = s.BigInt()
	}
	return sl
}

func iabs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

func imax(x, y int) int {
	if x > y {
		return x
	}
	return y
}

func imin(x, y int) int {
	if x < y {
		return x
	}
	return y
}

func ipow(x, n int) int {
	if n == 0 {
		return 1
	}
	a := ipow(x, n>>1)
	a *= a
	if n&1 != 0 {
		a *= x
	}
	return a
}

func chmax(x *int, v int) {
	if *x < v {
		*x = v
	}
}

func chmin(x *int, v int) {
	if *x > v {
		*x = v
	}
}

func factor(n int) map[int]int {
	m := map[int]int{}
	for i := 2; i*i <= n; i++ {
		for n%i == 0 {
			n /= i
			m[i]++
		}
	}
	if n != 1 {
		m[n]++
	}
	return m
}

var mod = 1000000007

func setMintMod(x int) {
	mod = x
}

type mint int

func newMint(v int) mint {
	return mint((v%mod + mod) % mod)
}

func (x mint) Add(y mint) mint {
	v := x + y
	if v >= mint(mod) {
		return v - mint(mod)
	}
	return v
}

func (x mint) Sub(y mint) mint {
	v := x + mint(mod) - y
	if v >= mint(mod) {
		return v - mint(mod)
	}
	return v
}

func (x mint) Mul(y mint) mint {
	return (x * y) % mint(mod)
}

func (x mint) pow(n int) mint {
	if n == 0 {
		return mint(1)
	}
	a := x.pow(n >> 1)
	a = a.Mul(a)
	if n&1 != 0 {
		a = a.Mul(x)
	}
	return a
}

func (x mint) Inverse() mint {
	return x.pow(mod - 2)
}

func (x mint) Div(y mint) mint {
	return x * y.Inverse()
}

func (x mint) Neg() mint {
	return newMint(int(-x))
}

type factorial struct {
	fact        []mint
	factInverse []mint
}

func newFactorial(n int) *factorial {
	f := new(factorial)
	f.init(n)
	return f
}

func (f *factorial) init(n int) {
	fact := make([]mint, n+1, n+1)
	fact[0] = newMint(1)
	for i := 1; i <= n; i++ {
		fact[i] = fact[i-1].Mul(newMint(i))
	}

	inv := make([]mint, n+1, n+1)
	inv[n] = fact[n].Inverse()
	for i := n; i >= 1; i-- {
		inv[i-1] = inv[i].Mul(newMint(i))
	}

	f.fact = fact
	f.factInverse = inv
}

func (f *factorial) Get(n int) mint {
	return f.fact[n]
}

func (f *factorial) GetInverse(n int) mint {
	return f.factInverse[n]
}

func (f *factorial) Permutation(n, k int) mint {
	if k < 0 || n < k {
		return 0
	}
	return f.fact[n].Mul(f.factInverse[n-k])
}

func (f *factorial) Combination(n, k int) mint {
	if k < 0 || n < k {
		return 0
	}
	return f.fact[n].Mul(f.factInverse[k]).Mul(f.factInverse[n-k])
}

type sieve struct {
	n          int
	primes     []int
	maxFactors []int
}

func newSieve(n int) *sieve {
	s := &sieve{
		n:          n,
		primes:     []int{},
		maxFactors: make([]int, n+1, n+1),
	}
	s.init()
	return s
}

func (s *sieve) init() {
	s.maxFactors[0] = -1
	s.maxFactors[1] = -1
	for i := 2; i <= s.n; i++ {
		if s.maxFactors[i] != 0 {
			continue
		}
		s.primes = append(s.primes, i)
		s.maxFactors[i] = i
		for j := i * i; j <= s.n; j += i {
			if s.maxFactors[j] == 0 {
				s.maxFactors[j] = i
			}
		}
	}
}

func (s *sieve) IsPrime(x int) bool {
	return s.maxFactors[x] == x
}

func (s *sieve) Factor(x int) map[int]int {
	m := map[int]int{}
	for x != 1 {
		m[s.maxFactors[x]]++
		x /= s.maxFactors[x]
	}
	return m
}