#include<iostream>

#include<fstream>

using namespace std;

void main()

{

  int a;

  int c;

  ifstream in ("abc.txt");

  in>>a;

  in.close();

  in.clear();

  ofstream file("abc.txt", ios::out | ios::app);

  file<<5;  //输入一个数如5

  file.close();

  file.clear();

  in.open("abc.txt");

  in>>c;

  in.close();

  in.clear();

  cout<<a<<endl;

  cout<<c<<endl;

}