DSA learning series

CodeChef-DSA-learners
,
1

DSA learning series week 2 4th question.
compiler and parsers.

I really don’t understand the problem with my code. can somebody please help.

#include
#include
#include
#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

int main() {

int t;
cin >> t;

while(t--){
    string str;
    cin >> str;
    
    int n = str.length();
    stack<char> s;
    int len = 0;
    int max = 0;
    int l = 0;
    
    for(int i = 0 ; i < n ; i++){
        if(str[i] == '<'){
            s.push('<');
        }
        else if(str[i] == '>'){
            if(s.empty()){
                len = 0;
                
            }
            else {
                s.pop();
            len += 2;
            if(len > max) max = len;
                
            }
        }
            
    }
    
    cout << max <<"\n";
    
}

return 0;

}

Atleast give me a test case where my code fails give the right answer. Any help is really appreciated