hi , here is my code . why my program crashed.

/// code

 import java.io.* ;
 import java.util.* ;

  public class stonepile {

  public static void main(String args[]) throwsIOException {

BufferedReader br = new BufferedReader(new  InputStreamReader(System.in));

    String str =null ;

   while((str=br.readLine())!=null) {
    //str=br.readLine() ;
   StringTokenizer st = new StringTokenizer(str," ") ;
   String s = st.nextToken() ;

      int []a = new int [50] ;
      int []dp =  new int [2000100] ;
      int  sum= 0 ;

       int n = Integer.parseInt(s) ;
         for ( int i = 0 ; i < n; i ++) {
           str = br.readLine() ;
             st = new StringTokenizer(str," ");
              s=st.nextToken() ;
              int m = Integer.parseInt(s) ;
               a[i] = m ;
                //sum +=m ;
          }

         dp[0] = 1 ;
          for ( int i = 0 ; i < n ; i++ ) {
              int c = a[i] ; sum+=c ;
            for ( int j = sum;  j -c >= 0 ; j--)
                 if ( dp[j-c]>0)
                      dp[ j ] = 1 ;

             }

          int y = -1 ,x = -1, j= -1 , r = 20000000 ;

            for ( int i = 1; i <sum+1 ; i++)
                 if ( dp[i]>0 && dp[sum-i]>0) {
                       x = Math.abs(i-(sum-i));
                       if ( r >x)
                           r=x  ;
             }

                    System.out.println(r) ;
           }
         }

      }