Problem:
Score : 300 points

Problem Statement

AtCoDeer the deer is seeing a quick report of election results on TV.
Two candidates are standing for the election: Takahashi and Aoki.
The report shows the ratio of the current numbers of votes the two candidates have obtained, but not the actual numbers of votes.
AtCoDeer has checked the report N times, and when he checked it for the i-th (1≦i≦N) time, the ratio was T_i:A_i.
It is known that each candidate had at least one vote when he checked the report for the first time.

Find the minimum possible total number of votes obtained by the two candidates when he checked the report for the N-th time.
It can be assumed that the number of votes obtained by each candidate never decreases.

Constraints

1≦N≦1000

1≦T_i,A_i≦1000 (1≦i≦N)

T_i and A_i (1≦i≦N) are coprime.

It is guaranteed that the correct answer is at most 10^{18}.

Input

The input is given from Standard Input in the following format:

N
T_1 A_1
T_2 A_2
:
T_N A_N

Output

Print the minimum possible total number of votes obtained by Takahashi and Aoki when AtCoDeer checked the report for the N-th time.

Sample Input 1

3
2 3
1 1
3 2

Sample Output 1

10

When the numbers of votes obtained by the two candidates change as 2,3 → 3,3 → 6,4, the total number of votes at the end is 10, which is the minimum possible number.

Sample Input 2

4
1 1
1 1
1 5
1 100

Sample Output 2

101

It is possible that neither candidate obtained a vote between the moment when he checked the report, and the moment when he checked it for the next time.

Sample Input 3

5
3 10
48 17
31 199
231 23
3 2

Sample Output 3

6930

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


import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

/**
 * Created by jaga on 9/22/16.
 */
public class Main{
    public static void solve(PrintWriter out, FastScanner in){
        int N = in.nextInt();
        long ansT = 1;//T川に入った票数
        long ansA = 1;//A側に入った票数

        for(int i =0 ;i < N;i++) {
            long pt = in.nextLong();
            long pa = in.nextLong();

            long m = Math.max(ansT / pt, ansA / pa);
            m = Math.max(1, m);

            long t = m * pt;
            long a = m  * pa;

            while (t < ansT || a < ansA) {
                t += pt;
                a += pa;
            }
            ansA = a;
            ansT = t;
        }
        System.out.println(ansA + ansT);
    }

    static class Pair implements Comparable {
        int first, second;

        Pair(int a, int b) {
            first = a;
            second = b;
        }

        public int compareTo(Object other) {
            Pair p1 = (Pair) other;
            return this.first - ((Pair) other).first; // IDの値に従い昇順で並び替えたい場合
//         return -(this.first - ((Pair) other).first); // IDの値に従い降順で並び替えたい場合
        }
    }

    /*以下はテンプレ*/
    public static void main(String args[]) {
        OutputStream outputStream = System.out;
        PrintWriter out = new PrintWriter(outputStream);
        FastScanner in = new FastScanner();
        solve(out, in);
        out.close();

    }

    public static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int bufferLength = 0;

        private boolean hasNextByte() {
            if (ptr < bufferLength) {
                return true;
            } else {
                ptr = 0;
                try {
                    bufferLength = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (bufferLength <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte()) return buffer[ptr++];
            else return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        private void skipUnprintable() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
        }

        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();
        }

        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();
            }
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        double[] nextDoubleArray(int n) {
            double[] array = new double[n];
            for (int i = 0; i < n; i++) {
                array[i] = nextDouble();
            }
            return array;
        }

        double[][] nextDoubleMap(int n, int m) {
            double[][] map = new double[n][];
            for (int i = 0; i < n; i++) {
                map[i] = nextDoubleArray(m);
            }
            return map;
        }

        public int nextInt() {
            return (int) nextLong();
        }

        public int[] nextIntArray(int n) {
            int[] array = new int[n];
            for (int i = 0; i < n; i++) array[i] = nextInt();
            return array;
        }

        public long[] nextLongArray(int n) {
            long[] array = new long[n];
            for (int i = 0; i < n; i++) array[i] = nextLong();
            return array;
        }

        public String[] nextStringArray(int n) {
            String[] array = new String[n];
            for (int i = 0; i < n; i++) array[i] = next();
            return array;
        }

        public char[][] nextCharMap(int n) {
            char[][] array = new char[n][];
            for (int i = 0; i < n; i++) array[i] = next().toCharArray();
            return array;
        }

        public int[][] nextIntMap(int n, int m) {
            int[][] map = new int[n][];
            for (int i = 0; i < n; i++) {
                map[i] = nextIntArray(m);
            }
            return map;
        }
    }
}