#include <iostream>
#include <vector>
const int INF = 1<<29;
using namespace std;

struct Node
{
    int v;
    int b,e,c;
    struct Node *next;
    Node()
    {
        next = NULL;
    }
};
vector<struct Node*> g(110);
int n,m,s,t,minT;
void dfs(int u,int reach,int Sbegin)
{
    int i,b,e,c,v;
    if(u==t)
    {
        if((reach - Sbegin)<minT)
            minT = reach - Sbegin;
        return;       
    }
    for(struct Node *p = g[u]->next;p!=NULL;p=p->next)
    {
        v = p->v;
        b = p->b;
        e = p->e;
        c = p->c;
        int uReach = reach;
        if(u==s)
        {
            if(b > 0)
            {
                Sbegin = b;
                uReach = b;
            }
        }
        int begin = uReach>b?uReach:b;
        if((e-begin)>=c && (begin+c-Sbegin)<minT)
        {
            dfs(v,begin+c,Sbegin);
        }
    }
}


int main()
{
    int i,u,v,b,e,c;
    cin>>n>>m>>s>>t;
    for(i=0;i<g.size();i++)
    {
        g[i] = new struct Node;
    }
    for(i=1;i<=m;i++)
    {
        cin>>u>>v>>b>>e>>c;
        struct Node *p;
        struct Node *temp = new struct Node;
        temp->v = v;
        temp->b = b;
        temp->e = e;
        temp->c = c;
        for(p = g[u];p->next!=NULL;p=p->next);
        p->next = temp;
        temp = new struct Node;
        temp->v = u;
        temp->b = b;
        temp->e = e;
        temp->c = c;
        for(p = g[v];p->next!=NULL;p=p->next);
        p->next = temp;
    }
    minT = INF;
    dfs(s,0,0);
    if(minT<INF)
        cout<<minT<<endl;
    else
        cout<<"Impossible"<<endl;
	return 0;
}