#include<deque>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define MAXN 50010
using namespace std;
int n,m,tot;
double l,r,mid;
double intrest[MAXN],cap[MAXN],dis[MAXN];
int to[MAXN],head[MAXN],net[MAXN],vis[MAXN],num[MAXN];
inline int read(){char ch=getchar();int data=0;while(ch<'0'||ch>'9') ch=getchar();do{data=data*10+ch-'0';ch=getchar();}while(ch>='0' && ch<='9');return data;
}
inline void add(int u,int v,double w,double p){to[++tot]=v;net[tot]=head[u];intrest[tot]=w;cap[tot]=p;head[u]=tot;
}
inline bool spfa(int s){deque<int>que;memset(vis,0,sizeof(vis));memset(num,0,sizeof(num));memset(dis,0x7f,sizeof(dis));que.push_back(s);dis[s]=0;vis[s]=1;num[s]++;while(!que.empty()){int now=que.front();que.pop_front();vis[now]=0;for(int i=head[now];i;i=net[i])if(dis[to[i]]>dis[now]+mid*cap[i]-intrest[i]){dis[to[i]]=dis[now]+mid*cap[i]-intrest[i];if(!vis[to[i]]){if(dis[to[i]]>dis[now])    que.push_back(to[i]);else    que.push_front(to[i]);vis[to[i]]=1;num[to[i]]++;if(num[to[i]]>n)    return true;}}}return false;
}
inline bool check(double x){if(spfa(0))    return true;else return false;
}
int main(){n=read();m=read();for(int i=1;i<=m;i++){int x,y;double v,p;x=read();y=read();scanf("%lf%lf",&v,&p);add(x,y,v,p);}for(int i=1;i<=n;i++)    add(0,i,0,0);l=0;r=500;while(r-l>0.01){mid=(l+r)/2;if(check(mid))    l=mid;else r=mid;}if(l==0)    cout<<"-1";else printf("%.1lf",r);
}