Black Friday

import java.util.ArrayList;
import java.util.Scanner;

class Heap<E extends Comparable<E>> {
    private E[] elements;

    public Heap(int size) {
        this.elements = (E[]) new Comparable[size];
    }

    int getParent(int i) {
        return (i + 1) / 2 - 1;
    }

    public E getAt(int i) {
        return this.elements[i];
    }

    int getLeft(int i) {
        return (i + 1) * 2 - 1;
    }

    int getRight(int i) {
        return (i + 1) * 2;
    }

    void setElement(int index, E elem) {
        this.elements[index] = elem;
    }

    void swap(int i, int j) {
        E tmp = this.elements[i];
        this.elements[i] = this.elements[j];
        this.elements[j] = tmp;
    }

    void adjust(int i, int n) {
        while(true) {
            if (i < n) {
                int left = this.getLeft(i);
                int right = this.getRight(i);
                int largest = i;
                if (left < n&&this.elements[left].compareTo(this.elements[i]) > 0) {
                    largest = left;
                }

                if (right < n && this.elements[right].compareTo(this.elements[largest]) > 0) {
                    largest = right;
                }

                if (largest != i) {
                    this.swap(i, largest);
                    i = largest;
                    continue;
                }
            }

            return;
        }
    }

    void buildHeap() {
        for(int i = this.elements.length / 2 - 1; i >= 0; --i) {
            this.adjust(i, this.elements.length);
        }

    }

    public void heapSort() {
        this.buildHeap();

        for(int i = this.elements.length - 1; i > 0; --i) {
            this.swap(0, i);
            this.adjust(0, i);
        }

    }
}

class Entry implements Comparable<Entry> {
    protected int vlez;
    protected int prestoj;

    public Entry(int v, int p) {
        this.vlez = v;
        this.prestoj = p;
    }

    public int vkupno() {
        return this.vlez + this.prestoj;
    }

    public int compareTo(Entry e) {
        if (this.vlez > e.vlez) {
            return 1;
        } else {
            return this.vlez < e.vlez ? -1 : 0;
        }
    }
}

public class BlackFriday {
    public BlackFriday() {
    }

    public static void main(String[] args) throws Exception {
        Scanner br = new Scanner(System.in);
        int N = Integer.parseInt(br.nextLine());
        Heap<Entry> heapDrvo = new Heap(N);

        for(int i = 0; i < N; ++i) {
            String s = br.nextLine();
            String[] pom = s.split(" ");
            String[] cas = pom[0].split(":");
            int vlez = Integer.parseInt(cas[0]) * 60 + Integer.parseInt(cas[1]);
            int prestoj = Integer.parseInt(pom[1]);
            Entry nov = new Entry(vlez, prestoj);
            heapDrvo.setElement(i, nov);
        }

        heapDrvo.heapSort();
        ArrayList<Entry> lista = new ArrayList(0);
        int max = 0;

        for(int i = 0; i < N; ++i) {
            for(int j = 0; j < lista.size(); ++j) {
                if (((Entry)lista.get(j)).vkupno() < ((Entry)heapDrvo.getAt(i)).vlez) {
                    lista.remove(j);
                }
            }

            lista.add((Entry)heapDrvo.getAt(i));
            if (lista.size() > max) {
                max = lista.size();
            }
        }

        System.out.println(max);
        br.close();
    }
}