Gem Stones - Less space solution

GemStones3.cs

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

namespace GemStone2
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            int n = Convert.ToInt16(s);

            string[] sA = new string[n];
            for (int i = 0; i < n; i++)
            {
                sA[i] = Console.ReadLine();
            }

            Console.WriteLine(getNumberOfGemElement(sA));
        }

        /*
         * string length >=1, <=100
         * only lower-cse Latin letters 'a'-'z'
         * 
         * string array size 1 - 100
         */
        public static int getNumberOfGemElement(string[] s)
        {
            int len = s.Length;

            int[] sumA = new int[26];            

            for (int i = 0; i < len; i++)
            {
                string s1 = s[i];
                // do not add same char twice 
                string countIn = ""; 
                foreach (char c in s1)
                {
                    if (!countIn.Contains(c.ToString()))
                    {
                        sumA[c - 'a']++;
                        countIn += c.ToString(); 
                    }                    
                }
            }

            int number = 0;
            for (int i = 0; i < 26; i++)
            {
                if (sumA[i] == len)
                    number++; 
            }

            return number;
        }
    }
}