#include <fstream>#include <stdio.h>#include <iostream>#include <string.h>#include <string>#include <limits.h>#include <algorithm>#include <math.h>#include <numeric>#include <functional>#include <ctype.h>#include <vector>using namespace std;const int kMAX=10010;const double kEPS=10E-6;vector<int> vec[kMAX];bool visit[kMAX];int ans,step[kMAX];void dfs(const int &x,const int &t){visit[x]=true;step[x]=t;for(size_t i=0;i<vec[x].size();++i){if(!visit[vec[x][i]])dfs(vec[x][i],t+1);elseans=max(ans,step[vec[x][i]]-step[x]+1);}}int main(void){ int n,m,ncase=1,u,v; scanf("%d",&ncase); while(~scanf("%d%d",&n,&m) && n) { for(int i=1;i<=n;++i) vec[i].clear();memset(visit,false,sizeof(visit));memset(step,0,sizeof(step));ans=0;while(m--){scanf("%d%d",&u,&v);vec[u].push_back(v);vec[v].push_back(u);}for(int i=1;i<=n;++i)if(!visit[i])dfs(i,0);printf("%dn",ans); } return 0;}
