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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    #region library
    static int n = 0;
    static int m = 0;
    static int r = 0;
    static int c = 0;
    static int x = 0;
    static int y = 0;
    static string s = "";
    static string[] ss;
    static long sum = 0;
    static long cnt = 0;
    static long max = -1;
    static long min = 2147483647;
    static bool flg = false;
    static bool flg2 = false;
    static string alpha = "abcdefghijklmnopqrstuvwxyz";
    static long mod = 1000000007;
    static long[] arr;
    static char[,] map;
    static long[,] imap;
    public class Input
    {
        static readonly char[] separator = { ' ', '\r', '\n' };
        readonly StreamReader sr;
        readonly Queue<string> queue;

        public Input(string path = "")
        {
            queue = new Queue<string>();

            if (string.IsNullOrEmpty(path))
            {
                sr = new StreamReader(Console.OpenStandardInput());
            }
            else
            {
                sr = new StreamReader(path);
            }
        }

        public void SetText(IEnumerable<string> items)
        {
            foreach (var item in items)
            {
                SetText(item);
            }
        }

        public bool SetText(string s)
        {
            if (s == null) return false;

            foreach (var elem in s.Trim()
                .Split(separator, StringSplitOptions.RemoveEmptyEntries))
            {
                queue.Enqueue(elem);
            }

            return true;
        }

        public bool Any()
        {
            return queue.Any() || Read();
        }

        bool Read()
        {
            if (!SetText(sr.ReadLine())) return false;

            if (!queue.Any()) return Read();

            return queue.Any();
        }

        public string Next()
        {
            if (!queue.Any() && !Read())
            {
                return "";
            }

            return queue.Dequeue();
        }

        bool Accumulate(int n)
        {
            while (queue.Count() < n)
            {
                if (!Read()) return false;
            }

            return true;
        }

        public int NextInt()
        {
            return int.Parse(Next());
        }
        public long NextLong()
        {
            return long.Parse(Next());
        }
        public double NextDouble()
        {
            return double.Parse(Next());
        }

        T[] NextT<T>(int n, T offset, Func<string, T> parse, Func<T, T, T> add)
        {
            if (!Accumulate(n)) return null;

            var a = new T[n];

            for (int i = 0; i < n; i++)
                a[i] = add(parse(queue.Dequeue()), offset);

            return a;
        }

        public string[] Next(int n)
        {
            return NextT(n, "", x => x, (x, y) => x);
        }
        public int[] NextInt(int n, int offset = 0)
        {
            return NextT(n, offset, int.Parse, (x, y) => x + y);
        }
        public long[] NextLong(int n, long offset = 0)
        {
            return NextT(n, offset, long.Parse, (x, y) => x + y);
        }
        public double[] NextDouble(int n, double offset = 0.0)
        {
            return NextT(n, offset, double.Parse, (x, y) => x + y);
        }
    }
    static Input input;
    static int Int()
    {
        return input.NextInt();
    }
    static long Long()
    {
        return input.NextLong();
    }
    static double Double()
    {
        return input.NextDouble();
    }
    static string Text()
    {
        return input.Next();
    }
    static void wl(object obj = null)
    {
        Console.WriteLine(obj);
    }
    static void w(object obj)
    {
        Console.Write(obj);
    }
    static void Yes()
    {
        wl("YES");
    }
    static void No()
    {
        wl("NO");
    }
    static void Sum()
    {
        wl(sum);
    }
    static void Cnt()
    {
        wl(cnt);
    }
    static void SetArray(long num = -1)
    {
        if (n == 0)
        {
            n = Int();
        }
        arr = new long[n];
        for (int i = 0; i < n; i++)
        {
            if (num == -1)
                arr[i] = Int();
            else
                arr[i] = num;
        }
    }
    static void ShowArray()
    {
        for (int i = 0; i < arr.Length; i++)
        {
            if (i > 0) w(" ");
            w(arr[i]);
        }
        wl();
    }
    static void SetMap(char def = '@')
    {
        if (r == 0 && c == 0)
        {
            r = Int();
            c = Int();
        }
        map = new char[r, c];
        for (int i = 0; i < r; i++)
        {
            if (def == '@') s = Text();
            for (int j = 0; j < c; j++)
            {
                map[i, j] = (def == '@') ? s[j] : def;
            }
        }
    }
    static void SetIMap(long def = -1)
    {
        if (r == 0 && c == 0)
        {
            r = Int();
            c = Int();
        }
        imap = new long[r, c];
        for (int i = 0; i < r; i++)
        {
            for (int j = 0; j < c; j++)
            {
                imap[i, j] = (def == -1) ? Int() : def;
            }
        }
    }
    static void ShowMap()
    {
        for (int i = 0; i < r; i++)
        {
            for (int j = 0; j < c; j++)
            {
                w(map[i, j]);
            }
            wl();
        }
    }
    static void ShowIMap()
    {
        for (int i = 0; i < r; i++)
        {
            for (int j = 0; j < c; j++)
            {
                w(imap[i, j]);
            }
            wl();
        }
    }
    #endregion

    #region main
    static void Main(string[] args)
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        input = new Input();
        Solve();
        Console.Out.Flush();
    }

    public static void Solve()
    {
        n = 5;
        SetArray();

        for (int i = 0; i < n; i++)
        {
            if (arr[i] == 0) wl(i + 1);

        }
        
    }

    #endregion
}