Объясните, как решать 23 егэ по информатике , (​

#include <iostream>
#include <string>
int main()
{
    using namespace std;

    //1й пункт
    string s1 = "Computer programming (often shortened to programming) is a process";
    for (int i = 2; i < s1.size(); i = i + 3)
        cout << s1[i];
    cout << endl;

    //2й пункт
    string s2 = "Programming involves activities such as analysis, developing understanding";
    for (int i = 1; i < s2.size(); i = i + 2)
        if (s2[i] != 'a' && s2[i] != 'b')
            s2[i] = 'a';
        else
            s2[i] = 'c';
    cout << s2 << endl;

    return 0;
}

1)
#include <iostream>
#include <conio.h>
#include <string>
using namespace std;
int main()
{
string str;
getline(cin, str);
for (int i = 1; i < str.length(); i++)
{
if (i % 3 == 0)
{cout << str[i] << endl;}
}
_getch();
return 0;
}
2)
#include <iostream>
#include <conio.h>
#include <string>
using namespace std;
int main()
{ string str;
getline(cin, str);
for (int i = 1; i < str.length(); i++)
{
 if (i % 2 == 0)
 { if (str[i] != 'a')
  { str[i] = 'a'; }
  if (str[i] != 'b')
  { str[i] = 'b'; }
  if (str[i] != 'c')
  { str[i] = 'c'; }
}
}
cout << str << endl;
_getch();
return 0;}