Language: C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <cstring>
#include <math.h>
#include <bitset>
#include <queue>
#include <set>
#include <iomanip>
#include <assert.h>
#include <cstdio>

// #include<bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr long long int INFLL = 1001001001001001LL;
constexpr long long int infll = 1001001001001001LL;
constexpr int INF = 1000000007;
constexpr int inf = 1000000007;
const int mod = 1000000007;

inline bool chmin(ll &a, ll b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}

inline bool chmax(ll &a, ll b)
{
    if (a < b)
    {
        a = b;
        return true;
    }
    return false;
}

template <typename T>
T seinomi(T a)
{
    if (a > 0)
    {
        return a;
    }
    else
    {
        return 0;
    }
}

//桁数取得
template <typename T>
T ketasuu(T num)
{
    return std::to_string(num).length();
}
//整数乗
ll llpow(ll a, ll n)
{
    if (n == 0)
    {
        return 1;
    }
    else
    {
        ll rep = a;
        for (ll i = 1; i < n; i++)
        {
            rep *= a;
        }
        return rep;
    }
}

template <class ForwardIt, class T>
void iota(ForwardIt first, ForwardIt last, T value)
{
    while (first != last)
    {
        *first++ = value;
        ++value;
    }
}

template <typename T>
T amarinasi(T a, T b)
{
    if (a % b == 0)
    {
        return a / b;
    }
    else if (a % b > 0)
    {
        return a / b + 1;
    }
    else
    {
        return a / b - 1;
    }
}

//小数点以下10桁テンプレート（main関数内の最初に貼付け）
//std::cout << std::fixed << std::setprecision(10);

//----------------------------------------------------------------
const double pi = 3.14159265358979323846264;

ll ans = 0;
ll n, c;
vector<pair<ll, ll>> data;

void dfs_pos2(ll cal, ll now, ll pre, ll turn, ll eat)
{
    cal += data[now].second;
    if (turn == 1)
    {
        cal -= llabs(data[now].first + (c - data[pre].first));
    }
    else
    {
        cal -= llabs(data[now].first - data[pre].first);
    }
    eat++;
    chmax(ans, cal);
    if (eat == n)
    {
        return;
    }
    dfs_pos2(cal, now + 1, now, turn + 1, eat);
}
void dfs_neg(ll cal, ll now, ll pre, ll turn, ll eat)
{
    cal += data[now].second;
    if (eat == 0)
    {
        cal -= c - data[now].first;
    }
    else
    {
        if (turn == 1)
        {
            cal -= llabs(data[pre].first + (c - data[now].first));
        }
        else
        {
            cal -= llabs((c - data[now].first) - (c - data[pre].first));
        }
    }

    eat++;
    chmax(ans, cal);
    if (eat == n)
    {
        return;
    }
    if (turn == 0)
    {
        dfs_pos2(cal, 0, now, turn + 1, eat);
        dfs_neg(cal, now - 1, now, turn, eat);
    }
    else
    {
        dfs_neg(cal, now - 1, now, turn + 1, eat);
    }
}
void dfs_pos1(ll cal, ll now, ll pre, ll turn, ll eat)
{
    cal += data[now].second;
    if (eat == 0)
    {
        cal -= data[now].first;
    }
    else
    {
        cal -= llabs(data[now].first - data[pre].first);
    }
    eat++;
    chmax(ans, cal);
    if (eat == n)
    {
        return;
    }
    if (turn == 0)
    {
        dfs_neg(cal, n - 1, now, turn + 1, eat);
        dfs_pos1(cal, now + 1, now, turn, eat);
    }
    else
    {
        dfs_pos1(cal, now + 1, now, turn + 1, eat);
    }
}
int main()
{
    cin >> n >> c;
    for (ll i = 0; i < n; i++)
    {
        ll tmp_x, tmp_v;
        cin >> tmp_x >> tmp_v;
        data.push_back(make_pair(tmp_x, tmp_v));
    }
    sort(data.begin(), data.end());

    dfs_pos1(0, 0, 0, 0, 0);
    dfs_neg(0, n - 1, n - 1, 0, 0);
    cout << ans << endl;
}

Compiler output:
a.cc: In function 'void dfs_pos2(ll, ll, ll, ll, ll)':
a.cc:119:12: error: reference to 'data' is ambiguous
  119 |     cal += data[now].second;
      |            ^~~~
In file included from /usr/include/c++/14/string:53,
                 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/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:122:22: error: reference to 'data' is ambiguous
  122 |         cal -= llabs(data[now].first + (c - data[pre].first));
      |                      ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:122:45: error: reference to 'data' is ambiguous
  122 |         cal -= llabs(data[now].first + (c - data[pre].first));
      |                                             ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:126:22: error: reference to 'data' is ambiguous
  126 |         cal -= llabs(data[now].first - data[pre].first);
      |                      ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:126:40: error: reference to 'data' is ambiguous
  126 |         cal -= llabs(data[now].first - data[pre].first);
      |                                        ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc: In function 'void dfs_neg(ll, ll, ll, ll, ll)':
a.cc:138:12: error: reference to 'data' is ambiguous
  138 |     cal += data[now].second;
      |            ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:141:20: error: reference to 'data' is ambiguous
  141 |         cal -= c - data[now].first;
      |                    ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:115:22: note:                 'std::vector<std::pair<long long int, long long int> > data'
  115 | vector<pair<ll, ll>> data;
      |                      ^~~~
a.cc:147:26: error: reference to 'data' is ambiguous
  147 |             cal -= llabs(data[pre].first + (c - data[now].first));
      |                          ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept