import java.util.*; import java.io.*; import java.math.*;
public class Main{
	static void solve(){//Here is the main function
		int N = nextInt();
		int M = nextInt();
		Node[] list = new Node[N];
		Edge[] E = new Edge[M];
		for(int i = 0; i < N; i++){
			list[i] = new Node(i);
		}
		for(int i = 0; i < M; i++){
			int u = nextInt() - 1;
			int v = nextInt() - 1;
			int c = nextInt();
			int d = nextInt();
			list[u].child.add(new Edge(i, v, c, d));
			list[v].child.add(new Edge(i, u, c, d));
		}
		PriorityQueue<Q> pq = new PriorityQueue<>();
		HashSet<Integer> usedEdge = new HashSet<>();
		pq.add(new Q(0, 0l, -1, -1));
		while(pq.size() > 0){
			Q now = pq.poll();
			int index = now.index;
			long cost = now.cost;
			int fromEdge = now.fromEdge;
			int fromNode = now.fromNode;
			if(list[index].firstCost != -1 && list[index].firstCost <= cost){
				continue;
			}
			list[index].firstCost = cost;
			list[index].lastEdge = fromEdge;
			list[index].lastNode = fromNode;
			ArrayList<Edge> child = list[index].child;
			for(int i = 0; i < child.size(); i++){
				Edge c = child.get(i);
				if(list[c.to].firstCost == -1){
					pq.add(new Q(c.to, cost + c.C, c.no, index));
				}else if(list[c.to].firstCost > cost + c.C){
					pq.add(new Q(c.to, cost + c.C, c.no, index));
				}
			}
		}
		int lastNode = N - 1;
		while(true){
			if(lastNode != -1){
				usedEdge.add(list[lastNode].lastEdge);
				lastNode = list[lastNode].lastNode;
			}else{
				break;
			}
		}
		myerr(list[N - 1].firstCost);
		pq.add(new Q(N - 1, 0l, -1, -1));
		while(pq.size() > 0){
			Q now = pq.poll();
			int index = now.index;
			long cost = now.cost;
			if(list[index].secondCost != -1 && list[index].secondCost <= cost){
				continue;
			}
			list[index].secondCost = cost;
			ArrayList<Edge> child = list[index].child;
			for(int i = 0; i < child.size(); i++){
				Edge c = child.get(i);
				if(usedEdge.contains(c.no)){
					c.C = c.D;
				}
				if(list[c.to].secondCost == -1){
					pq.add(new Q(c.to, cost + c.C, c.no, -1));
				}else if(list[c.to].secondCost > cost + c.C){
					pq.add(new Q(c.to, cost + c.C, c.no, -1));
				}
			}
		}
		myerr(list[0].secondCost);
		myout(list[0].secondCost + list[N - 1].firstCost);
		
	}
	//Method addition frame start

static class Q implements Comparable<Q>{
	int index;
	long cost;
	int fromEdge;
	int fromNode;
	Q(int index, long cost, int fromEdge, int fromNode){
		this.index = index;
		this.cost = cost;
		this.fromEdge = fromEdge;
		this.fromNode = fromNode;
	}
	public int compareTo(Q ato){
		return Long.compare(this.cost, ato.cost);
	}
}

static class Edge{
	int no;
	int to;
	int C;
	int D;
	Edge(int no, int to, int C, int D){
		this.no = no;
		this.to = to;
		this.C = C;
		this.D = D;
	}
}

static class Node{
	int no;
	int lastEdge = -1;
	int lastNode = -1;
	long firstCost = -1;
	long secondCost = -1;
	ArrayList<Edge> child = new ArrayList<>();
	Node(int no){
		this.no = no;
	}
}

	//Method addition frame end

	//Don't have to see. start------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			try{
				while((read = br.readLine()) != null){
					inputLine.addAll(Arrays.asList(read.split(" ")));
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object t){System.err.print("debug:");System.err.println(t);}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<String> nextStrArray(int size){
		ArrayList<String> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(next());
		}
		return ret;
	}
	static ArrayList<Integer> nextIntArray(int size){
		ArrayList<Integer> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(Integer.parseInt(next()));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(int size){
		ArrayList<Long> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(Long.parseLong(next()));
		}
		return ret;
	}
	@SuppressWarnings("unchecked")
	static String myconv(Object list, int no){//only join
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof ArrayList){
			return String.join(joinString, (ArrayList)list);
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//Don't have to see. end------------------------------------------
}