Input String and increment

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace string_rotation
{
    class Program
    {
        static void Main(string[] args)
        {
            //input string and increment
            string str = Console.ReadLine();
            string str1 = "";
            char[] c = str.ToCharArray();

            for (int i = 0; i < str.Length; i++)
            {
                char temp = ++c[i];
                if(temp == 'a' || temp == 'e' || temp =='i' || temp == 'o' || temp == 'u')
                {
                    str1 += temp.ToString().ToUpper();
                }
                else
                {
                    str1 += temp;
                }
            }
            Console.WriteLine(str1);

        }
    }
}