Calculate Serious Program Using Java

// serious program

import java.io.*;
class ssv123
{
public static void main(String args[]) throws IOException
{
int i,j,b,n;
String s;

DataInputStream a = new DataInputStream(System.in);
System.out.println("enter the number:");

s = a.readLine();
n=Integer.parseInt(s);

for(i=1;i<=n;i++)
{
for(j=1;j<=i;j++)
{
System.out.println(j + " ");
 }
}
for(i=n;i>=1;i--)
{
for(j=i;j>=1;j--)
{
System.out.println(i + " ");
 }
}
for(i=1;i<=n;i++)
{
for(j=1;j<=i;j++)
{
System.out.println(i + " ");
     }
    }
   }
}