public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int c = 0 , c1 = 0 ;
  int n = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) ;
  int [ ] [ ] l = new int [ 101 ] [ 101 ] ;
  while ( m -- > 0 ) {
    int a = sc . nextInt ( ) ;
    int b = sc . nextInt ( ) ;
    l [ a ] [ b ] = 1 ;
    l [ b ] [ a ] = 1 ;
    l [ a ] [ 0 ] ++ ;
    l [ b ] [ 0 ] ++ ;
  }
  Queue < Integer > q = new LinkedList < > ( ) ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) if ( l [ i ] [ 0 ] == 1 ) q . offer ( i ) ;
  while ( ! q . isEmpty ( ) ) {
    int size = q . size ( ) ;
    for ( int j = 0 ;
    j < size ;
    j ++ ) {
      int a = q . poll ( ) ;
      for ( int i = 0 ;
      i < 101 ;
      i ++ ) {
        if ( l [ a ] [ i ] == 1 ) {
          l [ a ] [ i ] = 0 ;
          l [ i ] [ a ] = 0 ;
          l [ i ] [ 0 ] -- ;
          l [ a ] [ 0 ] -- ;
        }
      }
    }
    for ( int i = 1 ;
    i <= n ;
    i ++ ) {
      if ( l [ i ] [ 0 ] == 1 ) {
        q . offer ( i ) ;
      }
    }
    c ++ ;
  }
  System . out . println ( c ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int c = 0 , c1 = 0 ; int n = sc . nextInt ( ) ; int m = sc . nextInt ( ) ; int [ ] [ ] l = new int [ 101 ] [ 101 ] ; while ( m -- > 0 ) { int a = sc . nextInt ( ) ; int b = sc . nextInt ( ) ; l [ a ] [ b ] = 1 ; l [ b ] [ a ] = 1 ; l [ a ] [ 0 ] ++ ; l [ b ] [ 0 ] ++ ; } Queue < Integer > q = new LinkedList < > ( ) ; for ( int i = 1 ; i <= n ; i ++ ) if ( l [ i ] [ 0 ] == 1 ) q . offer ( i ) ; while ( ! q . isEmpty ( ) ) { int size = q . size ( ) ; for ( int j = 0 ; j < size ; j ++ ) { int a = q . poll ( ) ; for ( int i = 0 ; i < 101 ; i ++ ) { if ( l [ a ] [ i ] == 1 ) { l [ a ] [ i ] = 0 ; l [ i ] [ a ] = 0 ; l [ i ] [ 0 ] -- ; l [ a ] [ 0 ] -- ; } } } for ( int i = 1 ; i <= n ; i ++ ) { if ( l [ i ] [ 0 ] == 1 ) { q . offer ( i ) ; } } c ++ ; } System . out . println ( c ) ; }
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