#include <iostream>
#include <fstream>
#include <string>
using namespace std;

void main()
{
    ifstream iFile("file.in");
    ofstream oFile("file.out");
    string line;

    int index = -1;
    while (iFile >> line)
    {
        index = line.find("Hello");
        if (index != string::npos)
            line.replace(index, sizeof("World") - 1, "World");
        oFile << line;
    }
    iFile.close();
    oFile.close();
}