#include<bits/stdc++.h>
using namespace std;
int m,n,a[20][20]={0},b[20][20]={0},a1[100010],b1[100010],a2=0,b2=0,x,y,p,q,a3,b3;
void dfs1(int s,int t){
    if (s==m){
        a1[++a2]=t;
    }else{
        for (int i=s+1;i<=m;i++){
            if (a[s][i]){
                dfs1(i,t+a[s][i]);
            }
        }
    }
}
void dfs2(int s,int t){
    if (s==m){
        b1[++b2]=t;
    }else{
        for (int i=s+1;i<=m;i++){
            if (b[s][i]){
                dfs2(i,t+b[s][i]);
            }
        }
    }
}
int main(){
    //freopen("meeting.in","r",stdin);
    //freopen("meeting.out","w",stdout);
    scanf("%d %d",&m,&n);
    for (int i=1;i<=n;i++){
        scanf("%d %d %d %d",&x,&y,&p,&q);
        a[x][y]=p;
        b[x][y]=q;
    }
    dfs1(1,0);
    dfs2(1,0);
    sort(a1+1,a1+a2+1);
    sort(b1+1,b1+b2+1);
    a3=1;b3=1;
    while (a3<=a2&&b3<=b2){
        if (a1[a3]==b1[b3]){
            cout<<a1[a3]<<endl;
            return 0;
        }else{
            if (a1[a3]<b1[b3]){
                a3++;
            }else{
                b3++;
            }
        }
    }
    cout<<"IMPOSSIBLE"<<endl;
    return 0;
}