input getting terminated for string input and vector operation without executing all requried loops

I am trying to do some string and vector operations, I want my for loop to execute n times but it terminates executing n-1 lines. suppose I gave input for the number of loops to be 5, it executes till 4 only times and terminates.;

this is my code which gives error;

#include<iostream>
#include<vector>
#include<string>
using namespace std;
int main(){
    int number_of_loop;
    vector<string>p;
    string elem;
    cin>>number_of_loop;
    cout<<"enter your strings for  loop now:";
    for(int i=0;i<number_of_loop;i++){
        getline(cin, elem);
        p.push_back(elem);
    }
    string y=p[0];
    cout<<"output are being printed"<<endl;
    cout<<y<<endl;
    cout<<y[1]<<endl;
    cout<<p[1][0]<<endl;
}

but this below code works perfectly fine where I have initialized number of loops before itself;

#include<iostream>
#include<vector>
#include<string>
using namespace std;
int main(){
    int number_of_loop=5;
    vector<string>p;
    string elem;
    cout<<"enter your strings for  loop now:";
    for(int i=0;i<number_of_loop;i++){
        getline(cin, elem);
        p.push_back(elem);
    }
    string y=p[0];
    cout<<"output are being printed"<<endl;
    cout<<y<<endl;
    cout<<y[1]<<endl;
    cout<<p[1][0]<<endl;
}

what goes wrong with my first code, please do help, thanks a lot.