string a = "abd";
            int count=0;
            char[] b = new char[] { 'a', 'f', 'g','a', 'b', 'd', 'o', 'c', 'a', 'v', 'g', 'h', 's' };
            for (int i = 0; i < b.Length - 1 - a.Length; i++)
            {
                if(a.Length==1 && a[i]==a[0] )
                {
                count++;
                }
                if (a.Length == 2 && b[i] == a[0]&& b[i+1]==a[1])
                {
                    count++;
                }
                if (a.Length == 3 && b[i] == a[0] && b[i + 1] == a[1] && b[i + 2] == a[2])
                {
                    count++;
                }
            }
            Console.WriteLine(count);