foo.cpp:10:13: error: 'sz' was not declared in this scope
 Node a[ 2 * sz ] , loser[ 2 * sz ] , winner[ 2 * sz ];
             ^
foo.cpp:10:31: error: 'sz' was not declared in this scope
 Node a[ 2 * sz ] , loser[ 2 * sz ] , winner[ 2 * sz ];
                               ^
foo.cpp:10:50: error: 'sz' was not declared in this scope
 Node a[ 2 * sz ] , loser[ 2 * sz ] , winner[ 2 * sz ];
                                                  ^
foo.cpp: In function 'int main()':
foo.cpp:15:18: error: 'a' was not declared in this scope
   scanf( "%d" , &a[ i ].mark );
                  ^
foo.cpp:19:18: error: 'a' was not declared in this scope
   scanf( "%d" , &a[ i ].s );
                  ^
foo.cpp:20:8: error: 'a' was not declared in this scope
  sort( a + 1 , a + 2 * n + 1 );
        ^
foo.cpp:29:5: error: 'winner' was not declared in this scope
     winner[ ++tw ] = a[ s ];
     ^
foo.cpp:30:5: error: 'loser' was not declared in this scope
     loser[ ++tl ] = a[ t ];
     ^
foo.cpp:33:5: error: 'winner' was not declared in this scope
     winner[ ++tw ] = a[ t ];
     ^
foo.cpp:34:5: error: 'loser' was not declared in this scope
     loser[ ++tl ] = a[ s ];
     ^
foo.cpp:41:9: error: 'winner' was not declared in this scope
    if ( winner[ tw ].mark > loser[ tl ].mark ) {
         ^
foo.cpp:41:29: error: 'loser' was not declared in this scope
    if ( winner[ tw ].mark > loser[ tl ].mark ) {
                             ^
foo.cpp:54:15: error: 'loser' was not declared in this scope
    a[ ++k ] = loser[ tl++ ];
               ^
foo.cpp:56:15: error: 'winner' was not declared in this scope
    a[ ++k ] = winner[ tw++ ];
               ^