static int countWays ( int num ) {
  int [ ] dp = new int [ num + 1 ] ;
  int MOD = ( int ) 1E9 + 7 ;
  dp [ 1 ] = 2 ;
  for ( int i = 2 ;
  i <= num ;
  ++ i ) {
    dp [ i ] = 0 ;
    for ( int j = 1 ;
    j <= 3 ;
    ++ j ) {
      if ( i - j == 0 ) dp [ i ] += 1 ;
      else if ( j == 1 ) dp [ i ] += dp [ i - j ] * 2 ;
      else if ( i - j > 0 ) dp [ i ] += dp [ i - j ] ;
      if ( dp [ i ] >= MOD ) dp [ i ] %= MOD ;
    }
  }
  return dp [ num ] ;
}

static int countWays ( int num ) { int [ ] dp = new int [ num + 1 ] ; int MOD = ( int ) 1E9 + 7 ; dp [ 1 ] = 2 ; for ( int i = 2 ; i <= num ; ++ i ) { dp [ i ] = 0 ; for ( int j = 1 ; j <= 3 ; ++ j ) { if ( i - j == 0 ) dp [ i ] += 1 ; else if ( j == 1 ) dp [ i ] += dp [ i - j ] * 2 ; else if ( i - j > 0 ) dp [ i ] += dp [ i - j ] ; if ( dp [ i ] >= MOD ) dp [ i ] %= MOD ; } } return dp [ num ] ; }
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