import java.io.IOException; import java.io.InputStream; import java.util.*; import java.util.function.BiFunction; import java.util.function.Function; import java.util.function.Supplier; public class Main { final static int INF = 1 << 28; final static long MOD = 1_000_000_007; final static double GOLDEN_RATIO = (1.0 + Math.sqrt(5)) / 2.0; Scanner sc = new Scanner(System.in); public static void main(String[] args) { new Main().run(); } void run() { int n = ni(); int a = ni(); for (int i = 1; i < n; ++i) { int v = ni(); int max = -INF; if (a / v > max) { max = a / v; } if (a - v > max) { max = a - v; } if (a + v > max) { max = a + v; } if (a * v > max) { max = a * v; } a = max; } System.out.println(a); } int ni() { return Integer.parseInt(sc.next()); } void debug(Object... os) { System.err.println(Arrays.deepToString(os)); } /** * ユークリッドの互除法 * * @return a と b の最大公約数 */ long gcd(long a, long b) { if (b == 0) { return a; } return gcd(b, a % b); } /** * 拡張ユークリッドの互除法 * * @return mx + ny = gcd(m, n)となるような(x, y)を返す */ Pair gcd_ex(long m, long n) { long[][] mat = _gcd_ex(m, n); return new Pair<>(mat[0][0], mat[0][1]); } long[][] _gcd_ex(long m, long n) { if (n == 0) { return new long[][]{{1, 0}, {0, 1}}; } long k = m / n; long[][] K = new long[][]{{0, 1}, {1, -k}}; long[][] r = _gcd_ex(n, m % n); long[][] dst = new long[2][2]; for (int y = 0; y < 2; ++y) for (int x = 0; x < 2; ++x) for (int i = 0; i < 2; ++i) dst[y][x] += r[y][i] * K[i][x]; return dst; } /** * 繰り返し2乗法を用いたべき乗の実装 * * @return a^r (mod 1,000,000,007) */ long pow(long a, long r) { long sum = 1; while (r > 0) { if ((r & 1) == 1) { sum *= a; sum %= MOD; } a *= a; a %= MOD; r >>= 1; } return sum; } /** * 組み合わせ * O(n) * * @return {}_nC_r */ long C(int n, int r) { long sum = 1; for (int i = n; 0 < i; --i) { sum *= i; sum %= MOD; } long s = 1; for (int i = r; 0 < i; --i) { s *= i; s %= MOD; } sum *= pow(s, MOD - 2); sum %= MOD; long t = 1; for (int i = n - r; 0 < i; --i) { t *= i; t %= MOD; } sum *= pow(t, MOD - 2); sum %= MOD; return sum; } /** * 黄金分割探索 * * @param left 下限 * @param right 上限 * @param f 探索する関数 * @param comp 上に凸な関数を探索するときは、Comparator.comparingDouble(Double::doubleValue) * 下に凸な関数を探索するときは、Comparator.comparingDouble(Double::doubleValue).reversed() * @return 極値の座標x */ double goldenSectionSearch(double left, double right, Function f, Comparator comp) { double c1 = divideInternally(left, right, 1, GOLDEN_RATIO); double c2 = divideInternally(left, right, GOLDEN_RATIO, 1); double d1 = f.apply(c1); double d2 = f.apply(c2); while (right - left > 1e-9) { if (comp.compare(d1, d2) > 0) { right = c2; c2 = c1; d2 = d1; c1 = divideInternally(left, right, 1, GOLDEN_RATIO); d1 = f.apply(c1); } else { left = c1; c1 = c2; d1 = d2; c2 = divideInternally(left, right, GOLDEN_RATIO, 1); d2 = f.apply(c2); } } return right; } /** * [a,b]をm:nに内分する点を返す */ double divideInternally(double a, double b, double m, double n) { return (n * a + m * b) / (m + n); } /** * http://alexbowe.com/popcount-permutations/ * bitの立っている数が小さい順にループしたいときに使う。 * ex) *
   * for (int i = 0; i < 25; ++i) {
   *   int bits = (1 << i) - 1;
   *   long m = C(25, num);
   *   for (j = 0; j < m; ++j) {
   *     ...(25個の中からi個bitが立っている)
   *     if (bits != 0)
   *       bits = next_perm(bits);
   *   }
   * }
   * 
* * @param v 現在のbit列 * @return 次のbit列 */ int next_perm(int v) { int t = (v | (v - 1)) + 1; return t | ((((t & -t) / (v & -v)) >> 1) - 1); } /** * http://qiita.com/p_shiki37/items/65c18f88f4d24b2c528b */ static class FastScanner { private final InputStream in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; public FastScanner(InputStream in) { this.in = in; } private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; } private boolean hasNextByte() { if (ptr < buflen) { return true; } else { ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1; } private void skipUnprintable() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; } public boolean hasNext() { skipUnprintable(); return hasNextByte(); } public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while (isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while (true) { if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; } else if (b == -1 || !isPrintableChar(b)) { return minus ? -n : n; } else { throw new NumberFormatException(); } b = readByte(); } } } class BIT { int n; ArrayList bit; BiFunction bif; /** * 1-indexed なBinary Indexed Treeを構築する * * @param n 容量 * @param bif 適用させる関数 * @param sup 初期値 */ BIT(int n, BiFunction bif, Supplier sup) { this.n = n; bit = new ArrayList<>(n + 1); for (int i = 0; i < n + 1; ++i) { bit.add(sup.get()); } this.bif = bif; } /** * iの位置の値をvで更新する * * @param i index * @param v 新しい値 */ void set(int i, T v) { for (int x = i; x <= n; x += x & -x) { bit.set(x, bif.apply(bit.get(x), v)); } } /** * クエリー * * @param defaultValue 初期値 * @param i index * @return [1, i]までfを適用した結果 */ T reduce(T defaultValue, int i) { T ret = defaultValue; for (int x = i; x > 0; x -= x & -x) { ret = bif.apply(ret, bit.get(x)); } return ret; } } class SegmentTree { int n; ArrayList dat; BiFunction bif; Supplier sup; /** * 0-indexed なSegment Treeを構築する * * @param n_ 要求容量 * @param bif 適用させる関数 * @param sup 初期値 */ SegmentTree(int n_, BiFunction bif, Supplier sup) { n = 1; while (n < n_) n *= 2; dat = new ArrayList<>(2 * n - 1); for (int i = 0; i < 2 * n - 1; ++i) { dat.add(sup.get()); } this.bif = bif; this.sup = sup; } /** * kの位置の値をvで更新する * * @param k index * @param v 新しい値 */ void set(int k, T v) { k += n - 1; dat.set(k, v); while (k > 0) { k = (k - 1) / 2; dat.set(k, bif.apply(dat.get(k * 2 + 1), dat.get(k * 2 + 2))); } } /** * クエリー * * @param l はじめ * @param r おわり * @return [l, r)での演算bifを適用した結果を返す */ T reduce(int l, int r) { return _reduce(l, r, 0, 0, n); } T _reduce(int a, int b, int k, int l, int r) { if (r <= a || b <= l) return sup.get(); if (a <= l && r <= b) return dat.get(k); T vl = _reduce(a, b, k * 2 + 1, l, (l + r) / 2); T vr = _reduce(a, b, k * 2 + 2, (l + r) / 2, r); return bif.apply(vl, vr); } } static class Pair, S extends Comparable> implements Comparable> { F f; S s; Pair() { } Pair(F f, S s) { this.f = f; this.s = s; } Pair(Pair p) { f = p.f; s = p.s; } @Override public int compareTo(Pair p) { if (f.compareTo(p.f) != 0) { return f.compareTo(p.f); } return s.compareTo(p.s); } @Override public int hashCode() { return f.hashCode() ^ s.hashCode(); } @Override public boolean equals(Object o) { if (this == o) { return true; } if (o == null || this.f == null || this.s == null) { return false; } if (this.getClass() != o.getClass()) { return false; } Pair p = (Pair) o; return this.f.equals(p.f) && this.s.equals(p.s); } @Override public String toString() { return "{" + f.toString() + ", " + s.toString() + "}"; } } }