Как отменить скролл у основного тела страницы и задать его элементу (модальному окну)?

body { 
	width: 100%; 
	height: 2000px; 
	overflow: hidden; /* скрывает скролл */ 
	padding: 0; 
	margin: 0; 
} 
 
.modal { 
	width: 400px; 
	height: 200px; 
	padding: 20px; 
	margin: 0 auto; 
	margin-top: 100px; 
    border: 1px solid #ccc; 
	overflow-y: scroll; /* применяет скролл к элементу */ 
	box-sizing: border-box; 
	background: #f1f1f1; 
}

<div class="modal"> 
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</div>