public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int N = in . nextInt ( ) ;
  int M = in . nextInt ( ) ;
  int [ ] minTime = new int [ N ] ;
  Arrays . fill ( minTime , Integer . MAX_VALUE ) ;
  int [ ] money = new int [ N ] ;
  for ( int m = 0 ;
  m < M ;
  m ++ ) {
    int L = in . nextInt ( ) - 1 ;
    int R = in . nextInt ( ) - 1 ;
    int T = in . nextInt ( ) ;
    int C = in . nextInt ( ) ;
    for ( int n = L ;
    n <= R ;
    n ++ ) {
      if ( T < minTime [ n ] ) {
        money [ n ] = C ;
        minTime [ n ] = T ;
      }
    }
  }
  int answer = 0 ;
  for ( int amount : money ) {
    answer += amount ;
  }
  System . out . println ( answer ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int N = in . nextInt ( ) ; int M = in . nextInt ( ) ; int [ ] minTime = new int [ N ] ; Arrays . fill ( minTime , Integer . MAX_VALUE ) ; int [ ] money = new int [ N ] ; for ( int m = 0 ; m < M ; m ++ ) { int L = in . nextInt ( ) - 1 ; int R = in . nextInt ( ) - 1 ; int T = in . nextInt ( ) ; int C = in . nextInt ( ) ; for ( int n = L ; n <= R ; n ++ ) { if ( T < minTime [ n ] ) { money [ n ] = C ; minTime [ n ] = T ; } } } int answer = 0 ; for ( int amount : money ) { answer += amount ; } System . out . println ( answer ) ; }
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