#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;
}