using System;

namespace assignments

{

    public class Stringocccurence

    {

        public static void Main(string[] args)

        {

        string s1;

        Console.Write("enter the string");

        s1=Console.ReadLine();

        string s2;

        Console.Write("enter the second  string");

        s2=Console.ReadLine();

        for(int i=0;i<s1.Length;i++)

        {

            char[] c=new char[100];

            c[i]=s1[i];

            if(c[i]=='a'||c[i]=='A')

            {

                s1=s1.Replace(c[i],'_');

            }

        }

        Console.WriteLine("the first string is{0}",s1);

            for(int i=0;i<s2.Length;i++)

        {

            char[] c=new char[100];

            c[i]=s2[i];

            if(c[i]=='a'||c[i]=='A')

            {

                s2=s2.Replace(c[i],'_');

            }

        }

        Console.WriteLine("the second string is{0}",s2);

        }

    }

}

​