Input some data and find the maximum output. (keyboard and file reading)

Keyboard entry , Until the input non number terminates

#include <iostream>

using namespace std;

int main()
{
    int i, j;
    cout << " Enter some data ：\n";
    cin >> i;
    int max = i;
    while (cin >> j)
    {
        if (j > max)
            max = j;
    }
    cout << " Maximum MAX = " << max << endl;
    return 0;
}

File read

#include<fstream>
#include<iostream>
using namespace std;
int main()
{
    ifstream in;
    ofstream out;

    int i, j, max;
    in.open("1.txt");
    out.open("2.txt");

    if (!in)
        cout << "1.txt Open the failure ！\n";
    if (!out)
        cout << "2.txt Open the failure ！\n";

    in >> i;
    max = i;
    while (in >> j)
    {
        if (j > max)
            max = j;
    }
    out << " Maximum MAX = " << max;

    return 0;
}