Problem:
Score : 200 points

Problem Statement

Takahashi lives in another world. There are slimes (creatures) of 10000 colors in this world. Let us call these colors Color 1, 2, ..., 10000.

Takahashi has N slimes, and they are standing in a row from left to right. The color of the i-th slime from the left is a_i.
If two slimes of the same color are adjacent, they will start to combine themselves. Because Takahashi likes smaller slimes, he has decided to change the colors of some of the slimes with his magic.

Takahashi can change the color of one slime to any of the 10000 colors by one spell.
How many spells are required so that no slimes will start to combine themselves?

Constraints

2 \leq N \leq 100

1 \leq a_i \leq N

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

Print the minimum number of spells required.

Sample Input 1

5
1 1 2 2 2

Sample Output 1

2

For example, if we change the color of the second slime from the left to 4, and the color of the fourth slime to 5, the colors of the slimes will be 1, 4, 2, 5, 2, which satisfy the condition.

Sample Input 2

3
1 2 1

Sample Output 2

0

Although the colors of the first and third slimes are the same, they are not adjacent, so no spell is required.

Sample Input 3

5
1 1 1 1 1

Sample Output 3

2

For example, if we change the colors of the second and fourth slimes from the left to 2, the colors of the slimes will be 1, 2, 1, 2, 1, which satisfy the condition.

Sample Input 4

14
1 2 2 3 3 3 4 4 4 4 1 2 3 4

Sample Output 4

4

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using static Asakatsu20200324A.Input;

namespace Asakatsu20200324A
{
    static class Input
    {
        private static Func<string, T[]> Cast<T>() => _ => _.Split(' ').Select(Convert<T>()).ToArray();

        private static Func<string, T> Convert<T>()
        {
            Type t = typeof(T);
            if (t == typeof(string)) return _ => (T) (object) _;
            if (t == typeof(int)) return _ => (T) (object) int.Parse(_);
            if (t == typeof(long)) return _ => (T) (object) long.Parse(_);
            if (t == typeof(double)) return _ => (T) (object) double.Parse(_);
            if (t == typeof(string[])) return _ => (T) (object) _.Split(' ');
            if (t == typeof(int[])) return _ => (T) (object) Cast<int>()(_);
            if (t == typeof(long[])) return _ => (T) (object) Cast<long>()(_);
            if (t == typeof(double[])) return _ => (T) (object) Cast<double>()(_);

            throw new NotSupportedException(t + "is not supported.");
        }

        private static T Convert<T>(string s) => Convert<T>()(s);

        private static string String() => Console.ReadLine();

        private static string[] String(long rowNumber) => new bool[rowNumber].Select(_ => String()).ToArray();

        public static void Cin<T>(out T a) => a = Convert<T>(String());

        public static void Cin<T1, T2>(out T1 a1, out T2 a2)
        {
            var v = String().Split(' ');
            set(v[0], out a1);
            set(v[1], out a2);
        }

        public static void Cin<T1, T2, T3>(out T1 a1, out T2 a2, out T3 a3)
        {
            var v = String().Split(' ');
            set(v[0], out a1);
            set(v[1], out a2);
            set(v[2], out a3);
        }

        public static void Cin<T1, T2, T3, T4>(out T1 a1, out T2 a2, out T3 a3, out T4 a4)
        {
            var v = String().Split(' ');
            set(v[0], out a1);
            set(v[1], out a2);
            set(v[2], out a3);
            set(v[3], out a4);
        }

        public static void Cin<T1, T2, T3, T4, T5>(out T1 a1, out T2 a2, out T3 a3, out T4 a4, out T5 a5)
        {
            var v = String().Split(' ');
            set(v[0], out a1);
            set(v[1], out a2);
            set(v[2], out a3);
            set(v[3], out a4);
            set(v[4], out a5);
        }

        public static void Cin<T1, T2, T3, T4, T5, T6>(out T1 a1, out T2 a2, out T3 a3, out T4 a4, out T5 a5, out T6 a6)
        {
            var v = String().Split(' ');
            set(v[0], out a1);
            set(v[1], out a2);
            set(v[2], out a3);
            set(v[3], out a4);
            set(v[4], out a5);
            set(v[5], out a6);
        }

        private static void set<T1>(string s, out T1 o1) => o1 = Convert<T1>(s);

        public static void Cin<T>(long n, out T[] l) => l = String(n).Select(Convert<T>()).ToArray();

        public static void Cin<T1, T2>(long n, out T1[] l1, out T2[] l2)
        {
            l1 = new T1[n];
            l2 = new T2[n];
            for (int i = 0; i < n; i++) Cin(out l1[i], out l2[i]);
        }

        public static void Cin<T1, T2, T3>(long n, out T1[] l1, out T2[] l2, out T3[] l3)
        {
            l1 = new T1[n];
            l2 = new T2[n];
            l3 = new T3[n];
            for (int i = 0; i < n; i++) Cin(out l1[i], out l2[i], out l3[i]);
        }

        public static void Cin<T1, T2, T3, T4>(long n, out T1[] l1, out T2[] l2, out T3[] l3, out T4[] l4)
        {
            l1 = new T1[n];
            l2 = new T2[n];
            l3 = new T3[n];
            l4 = new T4[n];
            for (int i = 0; i < n; i++) Cin(out l1[i], out l2[i], out l3[i], out l4[i]);
        }

        public static void Cin<T>(out T[] a) => a = Convert<T[]>(String());

        public static void Cin<T>(long h, out T[][] map) => map = String(h).Select(Convert<T[]>()).ToArray();
    }

    class Program
    {
        public static void Main(string[] args)
        {
            StreamWriter streamWriter = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            Console.SetOut(streamWriter);
            new Solver().Solve();
            Console.Out.Flush();
        }

        public static void Debug()
        {
            new Solver().Solve();
        }
    }

    class Solver
    {
        private long N;
        private long[] A;
        public void Solve()
        {
            Cin(out N);
            Cin(out A);

            long before = -1;
            long ans = 0;
            for (int i = 0; i < N; i++)
            {
                if (A[i] == before)
                {
                    ans++;
                    before = -1;
                    continue;
                }

                before = A[i];
            }

            Console.WriteLine(ans);
        }
    }
}