#include <iostream>

#include <algorithm>

using namespace std;

// Definition for a binary tree node.

struct TreeNode {

int val;

TreeNode *left;

TreeNode *right;

TreeNode(int x) : val(x), left(NULL), right(NULL) {}

};

static int x = []() {std::ios::sync_with_stdio(false); cin.tie(0); return 0; }();

class Solution

{

public:

int minDepth(TreeNode* root)

{

if (root == nullptr) return 0;

if (root->left == nullptr) return minDepth(root->right) + 1;

if (root->right == nullptr) return minDepth(root->left) + 1;

return min(minDepth(root->left) , minDepth(root->right)) + 1;

}

};