How can i solve certain challenges?

So i was having some fun at the challenges, but i got stuck in one, not because i wrote the code wrong, but because i can't understand how it works.

I couldn't do the problem #4 and #5.

https://onecompiler.com/challenges/3w8xvfbtb/strings-challenge

I'm using c++, and the print command (cout) don't print boolean as "true" or "false", but as "0" and "1", so i tried to make the code write "true" instead.
I think this may be the problem or not, because in both question #4 and #5 i got the first input right, but the second input is not accepted when i 'submit'.

What am I doing wrong?

Here is my code for problem #5:

(SPOILER | ANSWER)

---

https://onecompiler.com/cpp/3w95ru8sg

#include <iostream>
using namespace std;

int main()

{

string s; cin >> s;

bool b = false;

for (int n = 0; n < s.size(); ++n)

{

if (s[n] < 123 && s[n] > 97) { b = true; break; }

}

if (b) { cout << "true"; }

if (!b) { cout << "false"; }

return 0;

}

---

Consequence:

"
1/2 test cases passed

Test Case 1 passed

Test Case 2 failed
"