cpp6 understanding loops

#include<iostream>
using namespace std;


int main()
{
    int n;
    cin>>n;

    int sum=0;
    for(int counter=1;counter<=n;counter++){
        sum=sum+counter;
    }
    cout<<sum;
    
    
    
    int m;
    cin>>m;
    while(m>0){
        m=m+sum;
        
        cout<<m<<endl;
        cin>>m;
    }
    
    
    
    int x;
    cin>>x;
    do{
        x=x+m;
        cout<<x<<endl;
        cin>>x;
    }while(x>0);

    return 0;
}