#include<stdio.h>
#include<string.h>
const int inf=2147483647;
int abs(int x){return x>0?x:-x;}
int min(int a,int b){return a<b?a:b;}
int h[1010],cur[1010],nex[10010],to[10010],cap[10010],dis[1010],q[10010],M,S,T;
void add(int a,int b,int c){M++;to[M]=b;cap[M]=c;nex[M]=h[a];h[a]=M;M++;to[M]=a;cap[M]=0;nex[M]=h[b];h[b]=M;
}
bool bfs(){int head,tail,x,i;memset(dis,-1,sizeof(dis));head=tail=1;q[1]=S;dis[S]=0;while(head<=tail){x=q[head];head++;for(i=h[x];i;i=nex[i]){if(cap[i]&&dis[to[i]]==-1){dis[to[i]]=dis[x]+1;if(to[i]==T)return 1;tail++;q[tail]=to[i];}}}return 0;
}
int dfs(int x,int flow){if(x==T)return flow;int i,f;for(i=cur[x];i;i=nex[i]){if(cap[i]&&dis[to[i]]==dis[x]+1){f=dfs(to[i],min(flow,cap[i]));if(f){cap[i]-=f;cap[i^1]+=f;if(cap[i])cur[x]=i;return f;}}}dis[x]=-1;return 0;
}
int dicnic(){int ans=0,tmp;while(bfs()){memcpy(cur,h,sizeof(h));while(tmp=dfs(S,inf))ans+=tmp;}return ans;
}
int n,m,in[1010],ou[1010];
struct edge{int x,y,a,b;
}e[2010];
bool check(int lim){int i,s;memset(h,0,sizeof(h));memset(in,0,sizeof(in));memset(ou,0,sizeof(ou));M=1;for(i=1;i<=m;i++){if(e[i].a<=lim&&e[i].b<=lim){add(e[i].y,e[i].x,1);ou[e[i].x]++;in[e[i].y]++;}else if(e[i].a<=lim){ou[e[i].x]++;in[e[i].y]++;}else if(e[i].b<=lim){ou[e[i].y]++;in[e[i].x]++;}elsereturn 0;}s=0;for(i=1;i<=n;i++){if(abs(in[i]-ou[i])&1)return 0;if(in[i]<ou[i])add(i,T,(ou[i]-in[i])>>1);if(in[i]>ou[i]){add(S,i,(in[i]-ou[i])>>1);s+=(in[i]-ou[i])>>1;}}return s==dicnic();
}
int main(){int i,l,r,mid,ans;scanf("%d%d",&n,&m);for(i=1;i<=m;i++)scanf("%d%d%d%d",&e[i].x,&e[i].y,&e[i].a,&e[i].b);S=n+1;T=n+2;ans=-1;l=0;r=1000;while(l<=r){mid=(l+r)>>1;if(check(mid)){ans=mid;r=mid-1;}elsel=mid+1;}if(ans==-1)puts("NIE");elseprintf("%d",ans);
}