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.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
import java.lang.*;


public class Fourth{
	static long mod=1000000007;
	
    public static void main(String[] args) throws Exception{           	
    	 InputReader in = new InputReader(System.in);       
    	PrintWriter pw=new PrintWriter(System.out);   
    	
        double pi=3.14159265359;
        
            int n=in.readInt();
            double max=0;
            long [] v=new long[n];
            for(int j=0;j<n;j++){
            	int x=in.readInt();
            	int y=in.readInt();
            	//array[j]=s.nextDouble();
            	v[j]=(long)x*(long)x*(long)y;
            }

            TreeMap<Long, Long> d = new TreeMap<>();

            d.put(v[0], v[0]);
            for (int i = 1; i < n; i++)
            {
                Map.Entry<Long, Long> entry = d.lowerEntry(v[i]);
                
                long totalVolume = v[i];
                if (entry != null) {
                    totalVolume += entry.getValue();
                }
                
                d.put(v[i], totalVolume);
                for (Iterator<Map.Entry<Long, Long>> it = d.tailMap(v[i], false).entrySet().iterator();it.hasNext();) {
                    Map.Entry<Long, Long> greaterEntry = it.next();
                    if(greaterEntry.getValue() <= totalVolume) {
                        it.remove();
                    } else {
                        break;
                    }
                }
            }

            System.out.println(String.format("%.10f", d.lastEntry().getValue() * Math.PI));


    	pw.close();
    }





    
   
    public static BigInteger fact(int n)
    {
    	BigInteger x=BigInteger.valueOf(1);
    	for(int i=1;i<=n;i++)
    	{
    		x=x.multiply(BigInteger.valueOf(i));
    	}
    	return x;
    }
    /* returns nCr mod m */
   	public static long comb(long n, long r, long m) 
   	{
   		long p1 = 1, p2 = 1;
   		for (long i = r + 1; i <= n; i++) {
   			p1 = (p1 * i) % m;
   		}
   		p2 = factMod(n - r, m);
   		p1 = divMod(p1, p2, m);
   		return p1 % m;
   	}
   /* returns a/b mod m, works only if m is prime and b divides a */
   	public static long divMod(long a, long b, long m) 
   	{
   		long c = powerMod(b, m - 2, m);
   		return ((a % m) * (c % m)) % m;
   	}
   /* calculates factorial(n) mod m */
   	public static long factMod(long n, long m) {
   		long result = 1;
   		if (n <= 1)
   			return 1;
   		while (n != 1) {
   			result = ((result * n--) % m);
   		}
   		return result;
   	}
   /* This method takes a, b and c as inputs and returns (a ^ b) mod c */
   	public static long powerMod(long a, long b, long c) {
   		long result = 1;
   		long temp = 1;
   		long mask = 1;
   		for (int i = 0; i < 64; i++) {
   			mask = (i == 0) ? 1 : (mask * 2);
   			temp = (i == 0) ? (a % c) : (temp * temp) % c;
   			/* Check if (i + 1)th bit of power b is set */
   			if ((b & mask) == mask) {
   				result = (result * temp) % c;
   			}
   		}
   		return result;
   	}
	static boolean isPrime(int number) {
        if (number <= 1) {
            return false;
        }
        if (number <= 3) {
            return true;
        }
        if (number % 2 == 0 || number % 3 == 0) {
            return false;
        }
        int i = 5;
        while (i * i <= number) {
            if (number % i == 0 || number % (i + 2) == 0) {
                return false;
            }
            i += 6;
        }
        return true;
    }
	
public static long gcd(long x,long y)
{
	if(x%y==0)
		return y;
	else
		return gcd(y,x%y);
}
	
public static int gcd(int x,int y)
{
	if(x%y==0)
		return y;
	else 
		return gcd(y,x%y);
}
public static int abs(int a,int b)
{
	return (int)Math.abs(a-b);
}
public static long abs(long a,long b)
{
	return (long)Math.abs(a-b);
}
public static int max(int a,int b)
{
	if(a>b)
		return a;
	else
		return b;
}
public static int min(int a,int b)
{
	if(a>b)
		return b;
	else 
		return a;
}
public static long max(long a,long b)
{
	if(a>b)
		return a;
	else
		return b;
}
public static long min(long a,long b)
{
	if(a>b)
		return b;
	else 
		return a;
}

static boolean isPowerOfTwo (long v) {
	return (v & (v - 1)) == 0;
}
public static long pow(long n,long p,long m)
{
	 long  result = 1;
	  if(p==0)
	    return 1;
	if (p==1)
	    return n;
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;
	    if(result>=m)
	    result%=m;
	    p >>=1;
	    n*=n;
	    if(n>=m)
	    n%=m;
	}
	return result;
}
public static long pow(long n,long p)
{
	long  result = 1;
	  if(p==0)
	    return 1;
	if (p==1)
	    return n;
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;	    
	    p >>=1;
	    n*=n;	    
	}
	return result;

}
static class Pair implements Comparable<Pair>
{
	int a,b;
	Pair (int a,int b)
	{
		this.a=a;
		this.b=b;
	}

	public int compareTo(Pair o) {
		// TODO Auto-generated method stub
		if(this.a!=o.a)
		return Integer.compare(this.a,o.a);
		else
			return Integer.compare(this.b, o.b);
		//return 0;
	}
	public boolean equals(Object o) {
        if (o instanceof Pair) {
            Pair p = (Pair)o;
            return p.a == a && p.b == b;
        }
        return false;
    }
    public int hashCode() {
        return new Integer(a).hashCode() * 31 + new Integer(b).hashCode();
    }
} 
    
static long sort(int a[],int n)
{  	int b[]=new int[n];	
	return mergeSort(a,b,0,n-1);}
static long mergeSort(int a[],int b[],long left,long right)
{ long c=0;if(left<right)
 {   long mid=left+(right-left)/2;
	 c= mergeSort(a,b,left,mid);
	 c+=mergeSort(a,b,mid+1,right);
	 c+=merge(a,b,left,mid+1,right); }	
	return c;	 }
static long merge(int a[],int  b[],long left,long mid,long right)
{long c=0;int i=(int)left;int j=(int)mid; int k=(int)left;
while(i<=(int)mid-1&&j<=(int)right)
{ if(a[i]<=a[j]) {b[k++]=a[i++]; }
else	{ b[k++]=a[j++];c+=mid-i;}}
while (i <= (int)mid - 1)   b[k++] = a[i++]; 
while (j <= (int)right) b[k++] = a[j++];
for (i=(int)left; i <= (int)right; i++) 
	a[i] = b[i];  return c;  }
    
    
   static  class InputReader
    {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

        public InputReader(InputStream stream)
        {
            this.stream = stream;
        }

        public int read()
        {
            if (numChars == -1)
                throw new InputMismatchException();
            if (curChar >= numChars)
            {
                curChar = 0;
                try
                {
                    numChars = stream.read(buf);
                } catch (IOException e)
                {
                    throw new InputMismatchException();
                }
                if (numChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }

        public int readInt()
        {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-')
            {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do
            {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString()
        {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do
            {
                res.appendCodePoint(c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
        public double readDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, readInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, readInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }
        public long readLong() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }
        public boolean isSpaceChar(int c)
        {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next()
        {
            return readString();
        }

        public interface SpaceCharFilter
        {
            public boolean isSpaceChar(int ch);
        }
    }

     static class OutputWriter
    {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream)
        {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer)
        {
            this.writer = new PrintWriter(writer);
        }

        public void print(Object... objects)
        {
            for (int i = 0; i < objects.length; i++)
            {
                if (i != 0)
                    writer.print(' ');
                writer.print(objects[i]);
            }
        }

        public void printLine(Object... objects)
        {
            print(objects);
            writer.println();
        }

        public void close()
        {
            writer.close();
        }

        public void flush()
        {
            writer.flush();
        }

    }
    /* USAGE

    //initialize
        InputReader in 		= new InputReader(System.in);
        OutputWriter out	=	new OutputWriter(System.out);

    //read int
    int i = in.readInt();
    //read string
    String s = in.readString();
    //read int array of size N
    int[] x = IOUtils.readIntArray(in,N);
    //printline
    out.printLine("X");


    //flush output
    out.flush();

    //remember to close the
    //outputstream, at the end
    out.close();

    */
  static   class IOUtils {

        public static int[] readIntArray(InputReader in, int size) {
            int[] array = new int[size];
            for (int i = 0; i < size; i++)
                array[i] = in.readInt();
            return array;
    }
    }
//BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
	//StringBuilder sb=new StringBuilder("");
	 //InputReader in = new InputReader(System.in);
  // OutputWriter out = new OutputWriter(System.out);
	//PrintWriter pw=new PrintWriter(System.out);
	//String line=br.readLine().trim();
	       	
	//int t=Integer.parseInt(br.readLine());
  //	while(t-->0)
  	//{
  	//int n=Integer.parseInt(br.readLine());
	//long n=Long.parseLong(br.readLine());
	//String l[]=br.readLine().split(" ");
  //int m=Integer.parseInt(l[0]);
	//int k=Integer.parseInt(l[1]);
	//String l[]=br.readLine().split(" ");
	//l=br.readLine().split(" ");
	/*int a[]=new int[n];
	for(int i=0;i<n;i++)
	{
		a[i]=Integer.parseInt(l[i]);
	}*/
	   //System.out.println(" ");	     	
	
	//}
}