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<html><body><h1 id="demo">This is a Heading</h1><button type="button"onclick="document.getElementById('demo').innerHTML = 'Hello World!'">Click Me!</button></body></html><html><body><h1 id="demo">This is a Heading</h1><button type="button"onclick="document.getElementById('demo').innerHTML = 'Hello World!'">Click Me!</button></body></html>