随便写了个二分，样例输出 $0$，一交就过了。

#include <bits/stdc++.h>
#define int long long 
using namespace std;
const int N = 1e3 + 5;
int n, m, p[N][N], ans;
bool vis[N][N];
int dx[] = {-1, 1, 0, 0}, dy[] = {0, 0, -1, 1};
struct node{
	int x, y;
};
bool check (int mid){
	queue<node> q;
	memset (vis, 0, sizeof(vis));
	for (int i = 1; i <= n; ++i){
		q.push(node{1, i});
		vis[1][i] = 1;
	}
	while (!q.empty()){
		node tmp = q.front(); q.pop();
		int x = tmp.x, y = tmp.y;
		if (x == n) return 1;
		for (int i = 0; i < 4; ++i){
			int xx = x + dx[i], yy = y + dy[i];
			if (xx < 1 || xx > n || yy < 1 || yy > n || vis[xx][yy] || p[xx][yy] > mid) continue;
			vis[xx][yy] = 1;
			q.push(node{xx, yy});
			if (xx == n) return 1;
		}
	}
	return 0;
}
signed main (){
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	cin >> n >> m;
	int l = LONG_LONG_MAX, r = -1;
	for (int i = 1; i <= n; ++i){
		for (int j = 1; j <= m; ++j){
			cin >> p[i][j];
			l = min (l, p[i][j]);
			r = max (r, p[i][j]);
		}
	}
	while (l <= r){
		int mid = l + r >> 1;
		if (check(mid)){
			ans = mid;
			r = mid - 1;
		}else l = mid + 1;
	}	
	cout << ans << '\n';
	return 0;
}