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 A = RD-1;
		auto B = RD-1;
		auto C = RD;
		edges[A] ~= [B, C];
		edges[B] ~= [A, C];
	}
	auto T = RDA;

	long[][] q = [[0, T[0]]];
	auto dist = new long[][](N, 1002);
	foreach (i; 0..N)
		dist[i][] = long.max;
	dist[0][T[0]] = T[0];
	while (!q.empty)
	{
		auto node = q.front; q.popFront;
		auto u = node[0];
		auto p = node[1];
		auto d = dist[u][p];
		foreach (e; edges[u])
		{
			auto v = e[0];
			auto l = e[1];
			auto nd = T[v] + d + l / p;
			auto np = min(p + T[v], 1001);
			if (nd < dist[v][np])
			{
				dist[v][np] = nd;
				q ~= [v, np];
			}
		}
	}

	auto ans = dist[N-1].minElement;
	writeln(ans - T[N-1]);
	stdout.flush;
	debug readln;
}