#include <iostream>
#include <string>
#include <sstream>
#include <map>
int main() {
    std::string s;
    std::string n;
    std::string p;
    std::map<std::string,std::string> m;
    while(std::getline(std::cin,s)) {
        std::istringstream ss(s);
        ss>>n>>p;
        m.insert(std::make_pair(p,n));
    }
    if (m.size()==1) std::cout<<-1<<std::endl;
    else if (m.begin()->first.size()>m.rbegin()->first.size()) {
        std::cout<<m.begin()->second<<std::endl;
    }
    else {
        std::cout<<m.rbegin()->second<<std::endl;
    }
}