Language: C++

#include <iostream>
#include <algorithm>
#include <vector>

#define rep(i, n) for (int i = 0; i < n; ++i)
#define X first
#define Y second

using namespace std;

typedef pair<int, int> PII;
typedef pair<int, PII> P;
typedef vector<P> VP;

int main ( void )
{
  int n, m, a;
  while (cin >> n >> m >> a, n|m|a) {
    VP line(m), result(n);
    rep (i, n) { result[i] = i+1; }
    rep (i, m) {
      cin >> line[i].X >> line[i].Y.X >> line[i].Y.Y;
    }
    sort(line.begin(), line.end());
    rep (i, m) {
      swap(result[line[i].Y.X-1], result[line[i].Y.Y-1]);
    }
    rep (i, n) if (result[i] == a) {
      cout << i+1 << endl;
      break;
    }
  }
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:20:32: error: no match for 'operator=' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} and 'int')
   20 |     rep (i, n) { result[i] = i+1; }
      |                                ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_pair.h:946:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, const _U1&>, std::is_assignable<_T2&, const _U2&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(const std::pair<_U1, _U2>&) [with _U2 = _U1; _T1 = int; _T2 = std::pair<int, int>]'
  946 |         operator=(const pair<_U1, _U2>& __p)
      |         ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:946:9: note:   template argument deduction/substitution failed:
a.cc:20:32: note:   mismatched types 'const std::pair<_T1, _T2>' and 'int'
   20 |     rep (i, n) { result[i] = i+1; }
      |                                ^
/usr/include/c++/14/bits/stl_pair.h:957:9: note: candidate: 'template<class _U1, class _U2> typename std::enable_if<std::__and_<std::is_assignable<_T1&, _U1&&>, std::is_assignable<_T2&, _U2&&> >::value, std::pair<_T1, _T2>&>::type std::pair<_T1, _T2>::operator=(std::pair<_U1, _U2>&&) [with _U2 = _U1; _T1 = int; _T2 = std::pair<int, int>]'
  957 |         operator=(pair<_U1, _U2>&& __p)
      |         ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:957:9: note:   template argument deduction/substitution failed:
a.cc:20:32: note:   mismatched types 'std::pair<_T1, _T2>' and 'int'
   20 |     rep (i, n) { result[i] = i+1; }
      |                                ^
/usr/include/c++/14/bits/stl_pair.h:921:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<((bool)std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value), const std::pair<_T1, _T2>&, const std::__nonesuch&>) [with _T1 = int; _T2 = std::pair<int, int>; std::__conditional_t<((bool)std::__and_<std::is_copy_assignable<_T1>, std::is_copy_assignable<_T2> >::value), const std::pair<_T1, _T2>&, const std::__nonesuch&> = const std::pair<int, std::pair<int, int> >&]'
  921 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:923:65: note:   no known conversion for argument 1 from 'int' to 'std::__conditional_t<true, const std::pair<int, std::pair<int, int> >&, const std::__nonesuch&>' {aka 'const std::pair<int, std::pair<int, int> >&'}
  921 |       operator=(__conditional_t<__and_<is_copy_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
  922 |                                        is_copy_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  923 |                                 const pair&, const __nonesuch&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_pair.h:931:7: note: candidate: 'std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(std::__conditional_t<((bool)std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value), std::pair<_T1, _T2>&&, std::__nonesuch&&>) [with _T1 = int; _T2 = std::pair<int, int>; std::__conditional_t<((bool)std::__and_<std::is_move_assignable<_Tp>, std::is_move_assignable<_T2> >::value), std::pair<_T1, _T2>&&, std::__nonesuch&&> = std::pair<int, std::pair<int, int> >&&]'
  931 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:933:55: note:   no known conversion for argument 1 from 'int' to 'std::__conditional_t<true, std::pair<int, std::pair<int, int> >&&, std::__nonesuch&&>' {aka 'std::pair<int, std::pair<int, int> >&&'}
  931 |       operator=(__conditional_t<__and_<is_move_assignable<_T1>,
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  932 |                                        is_move_assignable<_T2>>::value,
      |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  933 |                                 pair&&, __nonesuch&&> __p)
      |                                 ~~~~~~~~~~~~~~~~~~~~~~^~~
a.cc:28:30: error: no match for 'operator==' (operand types are '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} and 'int')
   28 |     rep (i, n) if (result[i] == a) {
In file included from /usr/include/c++/14/iosfwd:42,
                 from /usr/include/c++/14/ios:40:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::fpos<_StateT>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::allocator<_CharT>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
In file included from /usr/include/c++/14/string:48:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::reverse_iterator<_Iterator>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::reverse_iterator<_Iterator>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::move_iterator<_IteratorL>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   '__gnu_cxx::__alloc_traits<std::allocator<std::pair<int, std::pair<int, int> > >, std::pair<int, std::pair<int, int> > >::value_type' {aka 'std::pair<int, std::pair<int, int> >'} is not derived from 'const std::move_iterator<_IteratorL>'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:28:33: note:   mismatched types 'const std::pair<_T1, _T2>' and 'int'
   28 |     rep (i, n) if (result[i] == a) {
      |                                 ^
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include