Error:System.FormatException: 'Input string was not in a correct format.'

I have a problem with C#

enter image description here
enter image description here this is what i am gonna do
I try to covert string to int, it still no active.

THIS IS MY FULL CODE!

using System;

namespace New
{
    class Program
    {
        public static string lastWord(string []a)
        {

            string word = a[0];

            foreach (string s in a)
                if (s > word) //ERROR
                {
                    word = s;
                }
            return word;
        }
        public static void Main(string[] args)
        {

            Console.WriteLine("Please enter 3 words, separated by a space: ");
            string input = Console.ReadLine();
            string[] nameArr = input.Split(" ");
            string name = lastWord(nameArr);
            Console.WriteLine("The word that comes last is " + name);
        }
    }
}

The compile error is telling you that you can't use the < operator with operands of type string.

In your case, since you're trying to find the last word in an array, you don't need to compare strings, you just need to get the last item from the array.

One way would be to walk through the array in a loop and re-assign the word for each item until you get to the end, and then return that item:

public static string LastWord(string[] input)
{
    // Handle some error cases as you see fit
    if (input == null) return null;
    if (input.Length == 0) return string.Empty;

    // Set word equal to the first string
    string word = input[0];

    // Loop through each item in the array
    for(int i = 1; i < input.Length; i++)
    {
        // Reset word to the current item
        word = input[i];
    }

    // Now word is the last item, so we can return it
    return word;
}

However, a faster way would be to use the .Length property of the array to determine the last index, and return the word at that index:

public static string LastWord(string[] input)
{
    // Handle some error cases as you see fit
    if (input == null) return null;
    if (input.Length == 0) return string.Empty;

    // Return the last string in the input array using 
    // the array's length to determine the last index
    return input[input.Length - 1];
}

And of course there's always Linq:

return input?.LastOrDefault();