About atom C++ string

#include<iostream>
# include <string>
using namespace std;
int main(void){
  US>string first_name;
  US>string last_name;
  US>string full_name;
  first_name = "Steve";
  last_name = "O";
  full_name = first_name + last_name;
  cout<<full_name<<endl;
  return 0;
}

#include<iostream>
using namespace std;

int main(void){
  inta,b;

  cin>>a>>b;

  if(a< b ){
    cout<<"a<b"<<endl;
  }
  else if(a>b){
    cout<<"a>b"<<endl;
  }
  else{
    cout<<"a==b"<<endl;
  }
  return 0;
}