var input = require('fs').readFileSync('/dev/stdin', 'utf8');
var lines = input.trim().split('\n');

var line;
while (line = lines.shift()) {
	var speed = +line;

	for (var f = 1;; f++) {
		var t = Math.sqrt((f * 5 - 5) / 4.9);
		var v = 9.8 * t;

		if (v >= speed) {
			console.log(f);
			break;
		}
	}
}