模拟一个森林，找森林的宽度和深度
#include <iostream>
using namespace std;
#include <vector>
#include <cstring>
int main(){
int n,m,a,b;
while (cin >> n>> m && n) {
vector<int> node[101]; // 找儿子
bool visited[101]; // 找爸爸 (是否有爸爸)
memset(visited, false, sizeof(visited));
bool twoFather = false, haveRoot = true;
for(int i = 0; i < m; ++i) {
cin >> a>> b;
node[a-1].push_back(b-1); // a的儿子有b
if (visited[b-1]) twoFather = true;
else visited[b-1] = true;
}
vector<int> next, now;
for (int i = 0; i < n; ++i) if (!visited[i]) now.push_back(i);
if (now.empty() || twoFather){
cout << "INVALID\n"; continue;
}
int depth = -1, width = 0, time = 0;
while(!now.empty() && time <= n+1) {
depth++;
if (now.size() > width) width = now.size();
for (int i = 0; i < now.size(); ++i) {
time++;
for (int j = 0; j < node[now[i]].size(); ++j) next.push_back(node[now[i]][j]);
}
now = next;
next.clear();
}
if (time == n){
cout << depth<< " "<< width<< endl;
} else {
cout << "INVALID\n";
}
}
}
