Factorial of a number not returning expected value

Question

I'm trying to pass a test case as below:

using System;
using System.Collections.Generic;
using NUnit.Framework;

[TestFixture]
public class SolutionTests
{

    [Test]
    public void Test1()
    {
        var solution = new Solution();

        Assert.AreEqual(solution.Factorial(5), 120);
    }

}

My code is returning 3125 and the expected answer is 120.

My code is below and I'm not sure why it's not working.

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

public class Solution
{
    public int Factorial(int input)
    {
        int result = 1;

        for (int i = 1; i <= input; i++)
        {
            result = result * input;
        }

        return result;
    }

}

I have looked at other similar examples but I'm struggling to understand them due to my learning difficulties can someone please help

Answer 1

You should multiply the result on i and not on input in the for loop like this:

for (int i = 1; i <= input; i++)
{
    result = result * i;
}