import java.io.*; import java.util.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); int m = sc.nextInt(); int[] heights = new int[n]; ArrayList> graph = new ArrayList<>(); ArrayList> reverse = new ArrayList<>(); for (int i = 0; i < n; i++) { heights[i] = sc.nextInt(); graph.add(new ArrayList<>()); reverse.add(new ArrayList<>()); } for (int i = 0; i < m; i++) { int a = sc.nextInt() - 1; int b = sc.nextInt() - 1; graph.get(a).add(b); reverse.get(b).add(a); } PriorityQueue queue = new PriorityQueue<>(); queue.add(new Path(0, 0, 0)); long[][] lefts = new long[2][n]; Arrays.fill(lefts[0], Long.MIN_VALUE); Arrays.fill(lefts[1], Long.MIN_VALUE); while (queue.size() > 0) { Path p = queue.poll(); if (lefts[p.type][p.idx] >= p.value) { continue; } lefts[p.type][p.idx] = p.value; for (int x : graph.get(p.idx)) { int nType; long nValue; if (heights[p.idx] < heights[x]) { if (p.type == 1) { continue; } nType = 1; nValue = p.value + heights[x] - heights[p.idx]; } else { nType = 0; nValue = p.value; } queue.add(new Path(x, nType, nValue)); } } if (lefts[0][n - 1] == Long.MIN_VALUE && lefts[1][n - 1] == Long.MIN_VALUE) { System.out.println(-1); } else { System.out.println(Math.max(lefts[0][n - 1], lefts[1][n - 1])); } queue.add(new Path(n - 1, 0, 0)); long[][] rights = new long[2][n]; Arrays.fill(rights[0], Long.MIN_VALUE); Arrays.fill(rights[1], Long.MIN_VALUE); while (queue.size() > 0) { Path p = queue.poll(); if (rights[p.type][p.idx] >= p.value) { continue; } rights[p.type][p.idx] = p.value; for (int x : reverse.get(p.idx)) { int nType; long nValue; if (heights[p.idx] < heights[x]) { if (p.type == 1) { continue; } nType = 1; nValue = p.value + heights[x] - heights[p.idx]; } else { nType = 0; nValue = p.value; } queue.add(new Path(x, nType, nValue)); } } if (rights[0][0] == Long.MIN_VALUE && rights[1][0] == Long.MIN_VALUE) { System.out.println(-1); } else { System.out.println(Math.max(rights[0][0], rights[1][0])); } } static class Path implements Comparable { int idx; int type; long value; public Path(int idx, int type, long value) { this.idx = idx; this.type = type; this.value = value; } public int compareTo(Path another) { if (value == another.value) { return 0; } else if (value < another.value) { return 1; } else { return -1; } } } } class Utilities { static String arrayToLineString(Object[] arr) { return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n")); } static String arrayToLineString(int[] arr) { return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new)); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); StringBuilder sb = new StringBuilder(); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public int[] nextIntArray() throws Exception { return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray(); } public String next() throws Exception { while (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }