#include <iostream>
#include <cstdio>
#include <string>
#include <map>
#include <vector>
#include <algorithm>

using namespace std;

int string_to_int(string a)
{
    reverse(a.begin(), a.end());
    int d = 1;
    int res = 0;
    for(int i = 0; i < a.size(); i++)
    {
        res += (a[i] - '0') * d;
        d *= 10;
    }
    return res;
}


double res_time(string a, int num)
{
    double minutes = string_to_int(a.substr(0, 2));
    double seconds = (double)string_to_int(a.substr(3, 2)) + ((double)string_to_int(a.substr(6, 1)) / 10);
    double res = minutes * 60 + seconds - num * 30;
    return res;
}

struct sman
{
    int time, start;
    string name;
    sman(): time(), start(), name(){}
    sman(int _time, int _start, string _name): time(_time), start(_start), name(_name){}
};

bool cmp (sman a, sman b)
{
    return a.time < b.time;
}



int main()
{
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int n;
    cin >> n;
    vector<sman> for_sort;
    map<string, int> res;
    map<int, string> finish;
    for(int i = 0; i < n; i++)
    {
        string name;
        cin >> name;
        string time;
        cin >> time;
        int t = res_time(time, -i);
        for_sort.push_back(sman(t, i, name));
    }
    sort(for_sort.begin(), for_sort.end(), cmp);
    for(int i = 0; i < n; i++)
    {
        int b = for_sort[i].time - for_sort[i].start * 2 * 30;
        finish[b] = for_sort[i].name;
        if(finish.begin()->first == b)
            res[finish[b]]++;
    }
    cout << res.size() << endl;
    for(auto it = res.begin(); it != res.end(); it++)
        cout << it->first << endl;
}