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코드 입니다 

import React from 'react';
import { Navbar,Nav,NavDropdown,Button,Jumbotron } from 'react-bootstrap';
import './App.css';

function App() {
return (
<div className="App">
<Navbar bg="light" expand="lg" className="">
<Navbar.Brand href="#home">Shoes shop</Navbar.Brand>
<Navbar.Toggle aria-controls="basic-navbar-nav" />
<Navbar.Collapse id="basic-navbar-nav">
<Nav className="mr-auto">
<Nav.Link href="#home">Home</Nav.Link>
<Nav.Link href="#link">Link</Nav.Link>
<NavDropdown title="Dropdown" id="basic-nav-dropdown">
<NavDropdown.Item href="#action/3.1">Action</NavDropdown.Item>
<NavDropdown.Item href="#action/3.2">Another action</NavDropdown.Item>
<NavDropdown.Item href="#action/3.3">Something</NavDropdown.Item>
<NavDropdown.Divider />
<NavDropdown.Item href="#action/3.4">Separated link</NavDropdown.Item>
</NavDropdown>
</Nav>
</Navbar.Collapse>
</Navbar>
<Jumbotron>
<h1>Hello, world!</h1>
<p>
This is a simple hero unit, a simple jumbotron-style component for calling
extra attention to featured content or information.
</p>
<p>
<Button variant="primary">Learn more</Button>
</p>
</Jumbotron>
</div>
);
}

export default App;