import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.bigint, std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

void chmin(T)(ref T x, T y) { x = min(x, y); } void chmax(T)(ref T x, T y) { x = max(x, y); }
bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
T lcm(T)(T x, T y) { return x * (y / gcd(x, y)); }

//long mod = 10^^9 + 7;
long mod = 998_244_353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }
void modpow(ref long x, long y) { if (!y) { x = 1; return; } auto t = x; x.modpow(y>>1); x.modm(x); if (y&1) x.modm(t); }
void modd(ref long x, long y) { y.modpow(mod - 2); x.modm(y); }

void main()
{
	auto N = RD;
	auto M = RD;
	auto edges = new long[][][](N);
	foreach (i; 0..M)
	{
		auto u = RD-1;
		auto v = RD-1;
		auto c = RD;
		auto d = RD;
		edges[u] ~= [v, c, d];
		edges[v] ~= [u, c, d];
	}

	long ans;
	{
		long[] q = [0];
		auto dist = new long[][](N);
		foreach (i; 0..N)
			dist[i] = [long.max, i];
		dist[0] = [0, 0];
		while (!q.empty)
		{
			auto u = q.front; q.popFront;
			foreach (e; edges[u])
			{
				auto v = e[0];
				auto d = e[1];
				auto nd = dist[u][0] + d;
				if (nd < dist[v][0])
				{
					dist[v] = [nd, u];
					q ~= v;
				}
			}
		}
		long pos = N-1;
		while (pos != 0)
		{
			auto prev = dist[pos][1];
			foreach (ref e; edges[pos])
			{
				if (e[0] == prev)
				{
					swap(e[1], e[2]);
					break;
				}
			}
			foreach (ref e; edges[prev])
			{
				if (e[0] == pos)
				{
					swap(e[1], e[2]);
					break;
				}
			}
			pos = prev;
		}
		ans += dist[N-1][0];
	}
	{
		long[] q = [N-1];
		auto dist = new long[][](N);
		foreach (i; 0..N)
			dist[i] = [long.max, i];
		dist[N-1] = [0, 0];
		while (!q.empty)
		{
			auto u = q.front; q.popFront;
			foreach (e; edges[u])
			{
				auto v = e[0];
				auto d = e[1];
				auto nd = dist[u][0] + d;
				if (nd < dist[v][0])
				{
					dist[v] = [nd, u];
					q ~= v;
				}
			}
		}
		ans += dist[0][0];
	}

	writeln(ans);
	stdout.flush;
	debug readln;
}