#include<bits/stdc++.h>
using namespace std;
int f[1001],head[1001];
struct node{
	int x,t;
};
int in,ui;
char ch;
int read()
{
	in=0;
	ch=getchar();
	ui=1;
	while(ch<'0'||ch>'9')
	{
		if(ch=='-')ui=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
	{
		in=in*10+ch-'0';
		ch=getchar();
	}
	return in*ui;
}
struct node2{
	int x,next;
}d[50001];
struct que{
	node a[2000001];
	int h,t;
	void del()
	{
		while(t>=h&&f[a[h].x])h++;
		while(t>=h&&f[a[t].x])t--;
	}
	bool empty(){del();return t<h;}
	void push(node x){a[++t]=x;}
	void pop(){h++;}
	node front(){del();return a[h];}
	void clear(){t=0,h=1;}
	int size(){del();return t-h+1;}
}q;
int ans;
void bfs(node x)
{
	q.push(x);
	while(!q.empty())
	{
		x=q.front();
		q.pop();
		ans=max(ans,x.t);
		f[x.x]=1;
		for(int i=head[x.x];i;i=d[i].next)
		{
			q.push(node{d[i].x,x.t+1});
		}
	}
}
int main()
{
	int n,m,x,y,k=0;
	for(;;)
	{
		n=read();
		m=read();
		if(n==0&&m==0)return 0;
		k=ans=0;
		memset(head,0,sizeof(head));
		for(int i=1;i<=m;i++)
		{
			x=read();
			y=read();
			k++;
			d[k]=node2{y,head[x]};
			head[x]=k;
			k++;
			d[k]=node2{x,head[y]};
			head[y]=k;
		}
		for(int i=1;i<=n;i++)
		{
			memset(f,0,sizeof(f));
			bfs(node{i,0});
		}
		printf("%d\n",ans*100);
	}
	return 0;
}