Revise paste Untitled

#include <iostream>
#include <vector>
#include <stack>
#include <cstring>
using namespace std;
int m ,k;
int n;
long long x;
class node{
public:
    node *a, *b;
    long long bitmask;
    node(){
        a = NULL;
        b = NULL;
        bitmask = 0;
    }
};
int ret;
string curr;
void rek(int at, int depth, node *tmp){
    tmp -> bitmask |= x;
    int popcount = __builtin_popcount(tmp -> bitmask);
    if(popcount == n && depth > ret){
        ret = depth;
    }
    if(at == (int)curr.size() || depth > 60){
        return;
    }
    if(curr[at] == 'a'){
        if(tmp -> a == NULL){
            tmp -> a = new node();
        }
        rek(at + 1, depth + 1, tmp -> a);
    }
    else{
        if(tmp -> b == NULL){
            tmp -> b = new node();
        }
        rek(at + 1, depth + 1, tmp -> b);
    }
}
int main(int argc, const char * argv[]) {
    ios_base::sync_with_stdio(false);
    cin >> n;
    string s[6];
    node *root = new node();
    for(int i =0; i < n; i ++){
        cin >> s[i];
    }
    for(int i =0; i < n; i ++){
        curr = s[i];
        x = (1 << i);
        for(int j =0; j < s[i].size(); j ++){
            rek(j, 0, root);
        }
    }
    cout << ret << endl;
    return 0;
}