#include <vector>
#include <algorithm>
#include <functional>

using namespace std;

struct compare_my : public binary_function<int, string, bool> {
    bool operator() (int i, string s) const {
    if (s[i]=='a') return true;
    return false;
    }
};
    


int main() {
    vector<string> vec;
    vec.push_back("ba");
    vec.push_back("ab");
    
    string* s=find_if(vec.begin(), vec.end(), bind1st(compare_my(), 1));
    cout << *s << endl;
}