Problem: As you know, every birthday party has a cake! This time, Babaei is going to prepare the very special birthday party's cake.

Simple cake is a cylinder of some radius and height. The volume of the simple cake is equal to the volume of corresponding cylinder. Babaei has n simple cakes and he is going to make a special cake placing some cylinders on each other.

However, there are some additional culinary restrictions. The cakes are numbered in such a way that the cake number i can be placed only on the table or on some cake number j where j < i. Moreover, in order to impress friends Babaei will put the cake i on top of the cake j only if the volume of the cake i is strictly greater than the volume of the cake j.

Babaei wants to prepare a birthday cake that has a maximum possible total volume. Help him find this value.

Input

The first line of the input contains a single integer n (1 ≤ n ≤ 100 000) — the number of simple cakes Babaei has.

Each of the following n lines contains two integers ri and hi (1 ≤ ri, hi ≤ 10 000), giving the radius and height of the i-th cake.

Output

Print the maximum volume of the cake that Babaei can make. Your answer will be considered correct if its absolute or relative error does not exceed 10 - 6.

Namely: let's assume that your answer is a, and the answer of the jury is b. The checker program will consider your answer correct, if <image>.

Examples

Input

2
100 30
40 10


Output

942477.796077000


Input

4
1 1
9 7
1 4
10 7


Output

3983.539484752

Note

In first sample, the optimal way is to choose the cake number 1.

In second sample, the way to get the maximum volume is to use cakes with indices 1, 2 and 4.

Solution (in JAVA):

Solution:
import java.util.*;
import java.io.*;
import java.math.BigDecimal;
import java.math.MathContext;
public class Main {
    static class Scan {
        private byte[] buf=new byte[1024];
        private int index;
        private InputStream in;
        private int total;
        public Scan()
        {
            in=System.in;
        }
        public int scan()throws IOException
        {
            if(total<0)
            throw new InputMismatchException();
            if(index>=total)
            {
                index=0;
                total=in.read(buf);
                if(total<=0)
                return -1;
            }
            return buf[index++];
        }
        public int scanInt()throws IOException
        {
            int integer=0;
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n))
            {
                if(n>='0'&&n<='9')
                {
                    integer*=10;
                    integer+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            return neg*integer;
        }
        public double scanDouble()throws IOException
        {
            double doub=0;
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            int neg=1;
            if(n=='-')
            {
                neg=-1;
                n=scan();
            }
            while(!isWhiteSpace(n)&&n!='.')
            {
                if(n>='0'&&n<='9')
                {
                    doub*=10;
                    doub+=n-'0';
                    n=scan();
                }
                else throw new InputMismatchException();
            }
            if(n=='.')
            {
                n=scan();
                double temp=1;
                while(!isWhiteSpace(n))
                {
                    if(n>='0'&&n<='9')
                    {
                        temp/=10;
                        doub+=(n-'0')*temp;
                        n=scan();
                    }
                    else throw new InputMismatchException();
                }
            }
            return doub*neg;
        }
        public String scanString()throws IOException
        {
            StringBuilder sb=new StringBuilder();
            int n=scan();
            while(isWhiteSpace(n))
            n=scan();
            while(!isWhiteSpace(n))
            {
                sb.append((char)n);
                n=scan();
            }
            return sb.toString();
        }
        private boolean isWhiteSpace(int n)
        {
            if(n==' '||n=='\n'||n=='\r'||n=='\t'||n==-1)
            return true;
            return false;
        }
    }
    
    public static void sort(int arr[],int l,int r) {    //sort(arr,0,n-1);
        if(l==r) {
            return;
        }
        int mid=(l+r)/2;
        sort(arr,l,mid);
        sort(arr,mid+1,r);
        merge(arr,l,mid,mid+1,r);
    }
    public static void merge(int arr[],int l1,int r1,int l2,int r2) {
        int tmp[]=new int[r2-l1+1];
        int indx1=l1,indx2=l2;
        //sorting the two halves using a tmp array
        for(int i=0;i<tmp.length;i++) {
            if(indx1>r1) {
                tmp[i]=arr[indx2];
                indx2++;
                continue;
            }
            if(indx2>r2) {
                tmp[i]=arr[indx1];
                indx1++;
                continue;
            }
            if(arr[indx1]<arr[indx2]) {
                tmp[i]=arr[indx1];
                indx1++;
                continue;
            }
            tmp[i]=arr[indx2];
            indx2++;
        }
        //Copying the elements of tmp into the main array
        for(int i=0,j=l1;i<tmp.length;i++,j++) {
            arr[j]=tmp[i];
        }
    }
    
    public static void sort(long arr[],int l,int r) {    //sort(arr,0,n-1);
        if(l==r) {
            return;
        }
        int mid=(l+r)/2;
        sort(arr,l,mid);
        sort(arr,mid+1,r);
        merge(arr,l,mid,mid+1,r);
    }
    public static void merge(long arr[],int l1,int r1,int l2,int r2) {
        long tmp[]=new long[r2-l1+1];
        int indx1=l1,indx2=l2;
        //sorting the two halves using a tmp array
        for(int i=0;i<tmp.length;i++) {
            if(indx1>r1) {
                tmp[i]=arr[indx2];
                indx2++;
                continue;
            }
            if(indx2>r2) {
                tmp[i]=arr[indx1];
                indx1++;
                continue;
            }
            if(arr[indx1]<arr[indx2]) {
                tmp[i]=arr[indx1];
                indx1++;
                continue;
            }
            tmp[i]=arr[indx2];
            indx2++;
        }
        //Copying the elements of tmp into the main array
        for(int i=0,j=l1;i<tmp.length;i++,j++) {
            arr[j]=tmp[i];
        }
    }
    
    
    

    static class seg_tree {
        long seg_tree[];
        public seg_tree(int n,long arr[]) {
            seg_tree=new long[4*n];
            create_seg_tree(arr,0,0,n-1);
        }

        //0 index-Left child-(2*i+1) Right Child-(2*i+2)

        public void create_seg_tree(long arr[],int vertex,int l,int r) {
            if(l==r) {
                seg_tree[vertex]=arr[r];
                return;
            }
            int mid=(l+r)/2;
            //Left Child
            create_seg_tree(arr,(2*vertex)+1,l,mid);
            //Right Child
            create_seg_tree(arr,(2*vertex)+2,mid+1,r);
            //Filling this node
            seg_tree[vertex]=Math.max(seg_tree[(2*vertex)+1],seg_tree[(2*vertex)+2]);
        }

        public long max(int vertex,int l,int r,int ql,int qr) {  //ql->query left , qr-> query right l->curr Segmrnt left    r->curr segment right
            if(ql>qr) {
                return 0;
            }

            if(ql==l && qr==r) {
                return seg_tree[vertex];
            }
            int mid=(l+r)/2;

            long max=Long.MIN_VALUE;

            //Left Child
            max=Math.max(max,max((2*vertex)+1,l,mid,ql,Math.min(qr, mid)));

            //Right Child
            max=Math.max(max,max((2*vertex)+2,mid+1,r,Math.max(mid+1,ql),qr));

            return max;
        }

        public void update(int vertex,int l,int r,int pos,long value) {   //pos->Position of the update   value->updates value
            if(l==r) {
                seg_tree[vertex]=value;
                return;
            }
            int mid=(l+r)/2;
            //Left Child
            if(pos<=mid) {
                update((2*vertex)+1,l,mid,pos,value);
            }
            //Right Child
            else {
                update((2*vertex)+2,mid+1,r,pos,value);
            }
            seg_tree[vertex]=Math.max(seg_tree[(2*vertex)+1],seg_tree[(2*vertex)+2]);
        }
    }

    
    
    
    
    
    public static void main(String args[]) throws IOException {
        Scan input=new Scan();
        int n=input.scanInt();
        long arr[]=new long[n];
        long brr[]=new long[n];
        
        for(int i=0;i<n;i++) {
            long tmp1=input.scanInt();
            long tmp2=input.scanInt();
            arr[i]=tmp1*tmp1*tmp2;
            brr[i]=arr[i];
        }
        sort(brr,0,n-1);
        long dp[]=new long[n];
        HashMap<Long,Integer> map=new HashMap<>();
        for(int i=0;i<n;i++) {
            map.put(brr[i], i);
        }
        seg_tree st=new seg_tree(n,dp);
        for(int i=0;i<n;i++) {
            int indx=map.get(arr[i]);
            int b_indx=search(brr,arr[i]);
            if(b_indx==-1) {
                dp[indx]=arr[i];
            }
            else {
                dp[indx]=Math.max(dp[indx],st.max(0, 0, n-1, 0, b_indx)+arr[i]);
            }
            st.update(0, 0, n-1, indx, dp[indx]);
        }
        long ans=0;
        for(int i=0;i<dp.length;i++) {
            ans=Math.max(ans,dp[i]);
        }
        
        BigDecimal tmp=new BigDecimal(""+ans);
        BigDecimal pi=new BigDecimal("3.1415926535897932384626433832795028841971693993751058209749445");
        BigDecimal fin=tmp.multiply(pi, MathContext.DECIMAL128);
        System.out.println(fin);
    }
    
    public static int search(long arr[],long val) {
        int l=0,r=arr.length-1,ans=-1;
        while(l<=r) {
            int mid=(l+r)/2;
            if(arr[mid]<val) {
                ans=mid;
                l=mid+1;
            }
            else {
                r=mid-1;
            }
        }
        return ans;
    }
}