I've written code for the Spy Life Code Coach. It works perfectly but the test cases come back wrong even though outputs match

Question

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

getline(cin,words);
int len=words.length();

for(int i=0;i<len;i++)
{
if (isalpha(words[i]) || words[i]==' ')
{
ans+=words[i];
}

}

//cout<<ans;
int lans=ans.length();
string output="";
for (int i=0; i<lans+1; i++)
{output+=ans[lans-i];}

cout<<output;

return 0;
}

*Why does it not work?*

Answer 1

Ah thanks I forgot the lans--;

Answer 2

I tried the -1. No difference. I can see my output is identical to expected output. For some reason it's still staying red though and not computing as correct...