The Spy Life. Why test do not check

Question

#include <iostream>
using namespace std;

int main() {
const int A = 65,
Z = 90,
a = 97,
z = 122,
space = 32;
string str, res;
getline(cin, str);
for (unsigned long int i = 0; i < str.length(); i++){
if (((str[i] >= A) && (str[i] <= Z)) || ((str[i] >= a) && (str[i] <= z)) || (str[i] == space)){
res += str[i];
}
}
int k = 0;
for (unsigned long int i = res.length() + 1; i > 0;){
cout<<res[--i];
}
return 0;
}

Answer 1

Use res.length(), instead of res.length()+1 & Try again....

And why need unsigned long int? int is enough..

Answer 2

The program gives the expected answer, but the test fails.

Answer 3

Jayakrishna, thank you

Answer 4

Imperator Teney you're welcome..