N programmers are going to participate in the preliminary stage of DDCC 20XX. Due to the size of the venue, however, at most 9 contestants can participate in the finals.

The preliminary stage consists of several rounds, which will take place as follows:

* All the N contestants will participate in the first round.
* When X contestants participate in some round, the number of contestants advancing to the next round will be decided as follows:
* The organizer will choose two consecutive digits in the decimal notation of X, and replace them with the sum of these digits. The number resulted will be the number of contestants advancing to the next round.
For example, when X = 2378, the number of contestants advancing to the next round will be 578 (if 2 and 3 are chosen), 2108 (if 3 and 7 are chosen), or 2315 (if 7 and 8 are chosen).
When X = 100, the number of contestants advancing to the next round will be 10, no matter which two digits are chosen.
* The preliminary stage ends when 9 or fewer contestants remain.



Ringo, the chief organizer, wants to hold as many rounds as possible. Find the maximum possible number of rounds in the preliminary stage.

Since the number of contestants, N, can be enormous, it is given to you as two integer sequences d_1, \ldots, d_M and c_1, \ldots, c_M, which means the following: the decimal notation of N consists of c_1 + c_2 + \ldots + c_M digits, whose first c_1 digits are all d_1, the following c_2 digits are all d_2, \ldots, and the last c_M digits are all d_M.

Constraints

* 1 \leq M \leq 200000
* 0 \leq d_i \leq 9
* d_1 \neq 0
* d_i \neq d_{i+1}
* c_i \geq 1
* 2 \leq c_1 + \ldots + c_M \leq 10^{15}

Input

Input is given from Standard Input in the following format:


M
d_1 c_1
d_2 c_2
:
d_M c_M


Output

Print the maximum possible number of rounds in the preliminary stage.

Examples

Input

2
2 2
9 1


Output

3


Input

3
1 1
0 8
7 1


Output

9
import java.io.*;
import java.sql.ClientInfoStatus;
import java.time.Year;
import java.util.*;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.function.BiPredicate;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

import static java.lang.Math.*;
import static java.lang.String.format;

public class Main {
    public static void main(String[] args) {
        solve();
    }
    final static long INF = Long.MAX_VALUE>>2;
    final static int MOD = 1_000_000_007;
    final static int[] dx4 = { 0, 1, 0, -1 };
    final static int[] dy4 = { 1, 0, -1, 0 };
    final static int[] dx9 = {-1, -1, -1,  0,  0, 0, 1, 1,1};
    final static int[] dy9 = {-1, 0, 1, -1, 0, 1, -1, 0,1};
    final static Runnable me=()->{};
    static int id=1;
    public static void solve(){
        //TODO:Solve problem like ***
        Scanner sc=new Scanner();
        int m = sc.nextInt();
        long[] d = new long[m];
        long[] c = new long[m];
        for (int i = 0; i < m; i++) {
            d[i] = sc.nextLong();
            c[i] = sc.nextLong();
        }
        long sum = IntStream.range(0, m).mapToLong(i -> d[i] * c[i]).sum();
        long cSum = Arrays.stream(c).sum();
        put(cSum - 1 + (sum - 1) / 9);




    }

    static class Accepter<T>{
        private T val;
        private final Predicate p;
        public Accepter(T defaultValue,Predicate p){
            this.val=defaultValue;
            this.p=p;
        }

        /**
         * @return accepted newval?
         */
        public boolean replace(T newVal){
            if(p.test(newVal)){
                this.val=newVal;
                return true;
            }
            return false;
        }
    }
    //runWhenEAで使う
    private static Runnable func(Object... objects){
        try{
            assert false;
            return me;
        }catch(AssertionError e){
            return ()->{put(objects);};
        }
    }
    private static void print(Object... objects){
        if(objects.length==1){
            System.out.print(objects[0]);
        }else{
            System.out.print(Arrays.toString(objects));
        }
    }
    private static void put(Object... objects) {
        print(objects);
        put();
    }
    private static void put(){
        System.out.println();
    }


    private static void runWhenEA(Runnable runnable){
        try{
            assert false;
        }catch(AssertionError e){
            PrintStream ps=System.out;
            PrintStream pse=System.err;
            System.setOut(pse);
            runnable.run();
            System.setOut(ps);
        }
    }
    private static void putM(String name,char[][] mat){
        put("---------------------"+name+"-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }
    private static void putM(String name,int[][] mat){
        put("---------------------"+name+"-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }
    private static void putM(String name,long[][] mat){
        put("---------------------"+name+"-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }
    private static void putM(String name,boolean[][] mat){
        put("---------------------"+name+"-----------------");
        for (int i = 0; i < mat.length; i++) {
            put(Arrays.toString(mat[i]));
        }
    }
    final static private class Scanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

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

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            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();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }
    }
    static private class FixedIntPair {
        final public int x, y;
        final static public FixedIntPair ZEROS=new FixedIntPair(0,0);
        FixedIntPair(int x, int y) {
            this.x = x;
            this.y = y;
        }
        @Override
        public String toString() {
            return format(FixedIntPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class FixedLongPair {
        final public long x, y;
        final static public FixedLongPair ZEROS=new FixedLongPair(0,0);
        FixedLongPair(long x, long y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public int hashCode() {
            return (int)x+(int)y;
        }

        @Override
        public boolean equals(Object obj) {
            if(obj==null)return false;
            if(!(obj instanceof FixedLongPair)) return false;
            FixedLongPair pair=(FixedLongPair)obj;
            return this.x==pair.x&&this.y==pair.y;
        }

        @Override
        public String toString() {
            return format(FixedLongPair.class.getSimpleName()+":(%d,%d)", x, y);
        }
    }
    final static private class Binary{
        public static String toZeroPadding(int i){
            return format("%"+Integer.toBinaryString(-1).length()+"s",Integer.toBinaryString(i)).replace(' ','0');
        }
        public static String toZeroPadding(long i){
            return format("%"+Long.toBinaryString(-1).length()+"s",Long.toBinaryString(i)).replace(' ','0');
        }
    }
    public static class BinaryIndexedTree {
        final int n;
        final long[] array;
        BinaryIndexedTree(long[] array){
            this.n=array.length;
            this.array=new long[n];
            for(int i=0;i<array.length;i++){
                add(i,array[i]);
            }
        }
        BinaryIndexedTree(int[] array){
            this.n=array.length;
            this.array=new long[n];
            for(int i=0;i<array.length;i++){
                add(i,array[i]);
            }
        }
        public void add(int index,long val){
            for(;index<n;index|=index+1){
                array[index]+=val;
            }
        }
        public long sum(int index){
            long result=0;
            for(;index>=0;index=(index&(index+1))-1){
                result+=array[index];
            }
            return result;
        }

        /**
         *
         * @param array arrayが1～nの順列になっていないならば定義されない
         * @return 転倒数
         */
        public static int inv(int[] array){
            int[] a=new int[array.length];
            BinaryIndexedTree bit=new BinaryIndexedTree(a);
            bit.add(array[0]-1,1);
            int result=0;
            for(int i=1;i<array.length;i++){
                System.out.println(bit);
                result+=i-bit.sum(array[i]-1);
                bit.add(array[i]-1,1);
            }
            return result;
        }

        @Override
        public String toString() {
            long[] array=new long[n];
            for(int i=0;i<n;i++){
                array[i]=sum(i);
            }
            String result="";
            result+="ruiseki:"+ Arrays.toString(array)+"\n";
            array[0]=sum(0);
            for(int i=1;i<n;i++){
                array[i]=sum(i)-sum(i-1);
            }
            result+="source::"+Arrays.toString(array);
            return result;
        }
    }

    final static private class Util {
        static long gcd(long a,long b){
            a= abs(a);
            b= abs(b);
            if(a<b){
                long tmp=a;
                a=b;
                b=tmp;
            }
            while(b!=0){
                long r=a%b;
                a=b;
                b=r;
            }
            return a;
        }
        static int gcd(int a,int b){
            a= abs(a);
            b= abs(b);
            if(a<b){
                int tmp=a;
                a=b;
                b=tmp;
            }
            while(b!=0){
                int r=a%b;
                a=b;
                b=r;
            }
            return a;
        }
        static long lcm(long a,long b){
            long gcd=gcd(a,b);
            long result=b/gcd;
            return a*result;
        }
        static boolean isValidCell(int i,int j,int h,int w){
            return i>=0&&i<h&&j>=0&&j<w;
        }
    }
}































































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 */
