public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int H = sc . nextInt ( ) ;
  int W = sc . nextInt ( ) ;
  int N = sc . nextInt ( ) ;
  LinkedList < Integer > [ ] block = new LinkedList [ W ] ;
  for ( int w = 0 ;
  w < W ;
  w ++ ) {
    block [ w ] = new LinkedList < > ( ) ;
    block [ w ] . add ( H ) ;
  }
  for ( int n = 0 ;
  n < N ;
  n ++ ) {
    int x = sc . nextInt ( ) - 1 ;
    int y = sc . nextInt ( ) - 1 ;
    block [ y ] . add ( x ) ;
  }
  for ( int w = 0 ;
  w < W ;
  w ++ ) Collections . sort ( block [ w ] ) ;
  int ans = 1000000 ;
  int curX = 0 ;
  for ( int w = 0 ;
  w < W ;
  w ++ ) {
    curX ++ ;
    while ( block [ w ] . peek ( ) < curX ) block [ w ] . poll ( ) ;
    ans = Math . min ( ans , block [ w ] . peek ( ) ) ;
    while ( w < W - 1 && block [ w + 1 ] . contains ( curX ) ) curX ++ ;
    if ( curX >= block [ w ] . peek ( ) ) break ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int H = sc . nextInt ( ) ; int W = sc . nextInt ( ) ; int N = sc . nextInt ( ) ; LinkedList < Integer > [ ] block = new LinkedList [ W ] ; for ( int w = 0 ; w < W ; w ++ ) { block [ w ] = new LinkedList < > ( ) ; block [ w ] . add ( H ) ; } for ( int n = 0 ; n < N ; n ++ ) { int x = sc . nextInt ( ) - 1 ; int y = sc . nextInt ( ) - 1 ; block [ y ] . add ( x ) ; } for ( int w = 0 ; w < W ; w ++ ) Collections . sort ( block [ w ] ) ; int ans = 1000000 ; int curX = 0 ; for ( int w = 0 ; w < W ; w ++ ) { curX ++ ; while ( block [ w ] . peek ( ) < curX ) block [ w ] . poll ( ) ; ans = Math . min ( ans , block [ w ] . peek ( ) ) ; while ( w < W - 1 && block [ w + 1 ] . contains ( curX ) ) curX ++ ; if ( curX >= block [ w ] . peek ( ) ) break ; } System . out . println ( ans ) ; }
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