Improving Time Hackerrank [terminated due to timeout]

Question

I've created code that based of the information that was given to me below.

"The first line will have an integer N denoting the number of entries in the phone book. Each entry consists of two lines: a name(either first-name or first-name last-name) and the corresponding phone number.

After these, there will be some queries. Each query will contain name of a friend. Read the queries until end-of-file."

Also if the name is not found you are supposed to print "Not found"

The problem is on Hackerrank.com and I cant submit because the program was "Terminated due to timeout"

Can someone please help me improve this code and make it run faster?! I barely figured out how to make it run so I'm all out of ideas on how to improve it.

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
using namespace std;

class Number{
    public:
    string name;
    string lname;
    long number;
};

class PhoneBook{
    public:
    void findNumber(){
        string tempName;
        while (cin >> tempName){
            int nf=0;
            for(int i=0; i < phoneNumbers.size(); i++){
                if (tempName == phoneNumbers[i].name){
                    cout << phoneNumbers[i].name << "=" << phoneNumbers[i].number << endl;
            }
            else {
                nf +=1;
            }
        }
        if (nf == phoneNumbers.size()){cout << "Not found" << endl;}
    }
}

void addNumber(int entries){
    for(int numbers = 0; numbers < entries; numbers++){
        Number newContact;
        long num;
        cin >> newContact.name;
        cin >> num;
        if (!cin){
            cin.clear();
            cin >> newContact.lname >> newContact.number;
            }
        else{
            newContact.number = num;
        }
        phoneNumbers.push_back(newContact);
    }
}

private:
string PBname;
vector<Number> phoneNumbers;
};


int main(){
    int entries;
    cin >> entries;
    PhoneBook myFriends;
    myFriends.addNumber(entries);
    myFriends.findNumber();
    return 0;
}