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import java.util.HashMap;
import java.util.Map;

class Solution {
    class Node {
        final int id;
        final Map<Integer, Node> neighborMap = new HashMap<>();
        int distanceFromNodeOne;

        public Node(int id) {
            this.id = id;
        }

        void addNeighbor(Node neighbor) {
            if (neighbor.id != id) {
                neighborMap.put(neighbor.id, neighbor);
            }
        }

        public String toString() {
            return "V[" + id + ": distanceFromNodeOne=" + distanceFromNodeOne + "]";
        }
    }

    public int solution(int n, int[][] edge) {
        Node[] nodes = new Node[n + 1];
        for (int i = 0; i <= n; i++) {
            nodes[i] = new Node(i);
        }

        for (int[] e : edge) {
            nodes[e[0]].addNeighbor(nodes[e[1]]);
            nodes[e[1]].addNeighbor(nodes[e[0]]);
        }

        boolean[] visited = new boolean[n + 1];
        dfs(nodes, visited, 1, 0);
        //TestHelper.printArray(nodes);

        int maxDistanceFromNodeOne = 0;
        Map<Integer, Integer> counterMap = new HashMap<>();
        for (Node node : nodes) {
            maxDistanceFromNodeOne = Math.max(maxDistanceFromNodeOne, node.distanceFromNodeOne);
            counterMap.compute(node.distanceFromNodeOne, (k, v) -> {
                if (v == null) return 1; else return v + 1;
            });
        }
//            TestHelper.log(maxDistanceFromNodeOne);
//            TestHelper.log(counterMap);
        if (maxDistanceFromNodeOne == 0) return 0;
        return counterMap.get(maxDistanceFromNodeOne);
    }

    private void dfs(Node[] nodes, boolean[] visited, int visit, int distance) {
        visited[visit] = true;
        Node nodeVisited = nodes[visit];
        if (nodeVisited.neighborMap.containsKey(1)) {
            nodeVisited.distanceFromNodeOne = 1;
        } else {
            nodeVisited.distanceFromNodeOne = distance;
        }
        for (int neighbor : nodeVisited.neighborMap.keySet()) {
            if (visited[neighbor]) {
                nodes[neighbor].distanceFromNodeOne = Math.min(nodeVisited.distanceFromNodeOne + 1, nodes[neighbor].distanceFromNodeOne); 
            } else {
                dfs(nodes, visited, neighbor, nodeVisited.distanceFromNodeOne + 1);
            }
        }
    }
}