Fibonacci series

int[] arr1 = { 1, 2, 100 }; // Take Array with 3 elements

int n1, n2; //Take 2 variables
n1 = n2 = arr1[0];
Console.WriteLine(n1);
            
while (n2 < arr1[2])
{
    Console.WriteLine(n2);
    n2 += n1;
    n1 = n2 - n1;
}

Console.ReadLine();