Problem:
Score : 500 points

Problem Statement

Given are N positive integers A_1,...,A_N.

Consider positive integers B_1, ..., B_N that satisfy the following condition.

Condition: For any i, j such that 1 \leq i < j \leq N, A_i B_i = A_j B_j holds.

Find the minimum possible value of B_1 + ... + B_N for such B_1,...,B_N.

Since the answer can be enormous, print the sum modulo (10^9 +7).

Constraints

1 \leq N \leq 10^4

1 \leq A_i \leq 10^6

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

Print the minimum possible value of B_1 + ... + B_N for B_1,...,B_N that satisfy the condition, modulo (10^9 +7).

Sample Input 1

3
2 3 4

Sample Output 1

13

Let B_1=6, B_2=4, and B_3=3, and the condition will be satisfied.

Sample Input 2

5
12 12 12 12 12

Sample Output 2

5

We can let all B_i be 1.

Sample Input 3

3
1000000 999999 999998

Sample Output 3

996989508

Print the sum modulo (10^9+7).

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)


import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Main {
  private static void solve() {
    int n = ni();
    int[] a = na(n);
    int[] primes = sieveEratosthenes(1000000);

    int[][][] f = new int[n][][];
    Map<Integer, Integer> cnt = new HashMap<>();
    Map<Integer, Integer> max = new HashMap<>();

    for (int i = 0; i < n; i++) {
      f[i] = factor(a[i], primes);
      for (int[] g : f[i]) {
        cnt.putIfAbsent(g[0], 0);
        max.putIfAbsent(g[0], 0);
        cnt.put(g[0], cnt.get(g[0]) + g[1]);
        max.put(g[0], Math.max(max.get(g[0]), g[1]));
      }
    }

    int mod = (int) 1e9 + 7;
    long gcd = 1;
    for (int v : cnt.keySet()) {
      int k = cnt.get(v) - max.get(v);
      for (int i = 0; i < k; i++) {
        gcd *= v;
        gcd %= mod;
      }
    }

    long base = invl(gcd, mod);
    for (int v : a) {
      base *= v;
      base %= mod;
    }

    long ret = 0;
    for (int v : a) {
      ret += base * invl(v, mod) % mod;
      ret %= mod;
    }
    System.out.println(ret);
  }

  public static long invl(long a, long mod) {
    long b = mod;
    long p = 1, q = 0;
    while (b > 0) {
      long c = a / b;
      long d;
      d = a;
      a = b;
      b = d % b;
      d = p;
      p = q;
      q = d - c * q;
    }
    return p < 0 ? p + mod : p;
  }


  public static int[] sieveEratosthenes(int n) {
    if (n <= 32) {
      int[] primes = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31};
      for (int i = 0; i < primes.length; i++) {
        if (n < primes[i]) {
          return Arrays.copyOf(primes, i);
        }
      }
      return primes;
    }

    int u = n + 32;
    double lu = Math.log(u);
    int[] ret = new int[(int) (u / lu + u / lu / lu * 1.5)];
    ret[0] = 2;
    int pos = 1;

    int[] isnp = new int[(n + 1) / 32 / 2 + 1];
    int sup = (n + 1) / 32 / 2 + 1;

    int[] tprimes = {3, 5, 7, 11, 13, 17, 19, 23, 29, 31};
    for (int tp : tprimes) {
      ret[pos++] = tp;
      int[] ptn = new int[tp];
      for (int i = (tp - 3) / 2; i < tp << 5; i += tp)
        ptn[i >> 5] |= 1 << (i & 31);
      for (int j = 0; j < sup; j += tp) {
        for (int i = 0; i < tp && i + j < sup; i++) {
          isnp[j + i] |= ptn[i];
        }
      }
    }

    // 3,5,7
    // 2x+3=n
    int[] magic = {0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13, 31, 22, 28, 18, 26, 10,
        7, 12, 21, 17, 9, 6, 16, 5, 15, 14};
    int h = n / 2;
    for (int i = 0; i < sup; i++) {
      for (int j = ~isnp[i]; j != 0; j &= j - 1) {
        int pp = i << 5 | magic[(j & -j) * 0x076be629 >>> 27];
        int p = 2 * pp + 3;
        if (p > n)
          break;
        ret[pos++] = p;
        if ((long) p * p > n)
          continue;
        for (int q = (p * p - 3) / 2; q <= h; q += p)
          isnp[q >> 5] |= 1 << q;
      }
    }

    return Arrays.copyOf(ret, pos);
  }

  public static int[][] factor(int n, int[] primes) {
    int[][] ret = new int[9][2];
    int rp = 0;
    for (int p : primes) {
      if (p * p > n)
        break;
      int i;
      for (i = 0; n % p == 0; n /= p, i++);
      if (i > 0) {
        ret[rp][0] = p;
        ret[rp][1] = i;
        rp++;
      }
    }
    if (n != 1) {
      ret[rp][0] = n;
      ret[rp][1] = 1;
      rp++;
    }
    return Arrays.copyOf(ret, rp);
  }

  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}