using System;

public class Program

{

    public static void Main()

    {

    }

    public string LongestCommonPrefix(string[] strs) {

        Dictionary<int, char[]> dict = new Dictionary<int, char[]>(); 

        bool flag= false;

        char firstChar;

        string res="";

        if (strs == null || strs.Length<1)

            return res;

        else{

            int strsLength= strs.Length, minString= strs[0].Length;

            for(int i=1; i<strsLength; i++)

                if(strs[i].Length< minString)

                    minString = strs[i].Length;

            for(int i=0; i<strsLength; i++)

                dict.Add(i, strs[i].ToCharArray());

            firstChar= dict[0][0];

            for(int i=1; i<strsLength; i++){

                if(firstChar == dict[i][0]){

                    flag= true;

                }

                else{

                    return res;

                }

            }

            if(flag)

                res+= dict[0][0];

            else

                res = "";

            for(int i=1; i< minString; i++){

                firstChar = dict[0][i];

                int j=1;

                for( j=1; j<strsLength; j++){

                    if(firstChar == dict[j][i])

                        flag = true;

                    else{

                        return res;

                    }

                }

                if(flag)

                    res+= dict[0][i];

                else

                    return res;

            }

            return res;

        }

    }

}