#include "bits/stdc++.h"
constexpr int __FREAD__ = 0;
constexpr char __FIN__[] = "";
constexpr char __FOUT__[] = "";
constexpr bool MTS = false;
constexpr bool SPC_MTS = false;
#define _LOAD_4(a, b, c, d, ...) d
#define _ALL_0(arg) begin(arg), end(arg)
#define _ALL_1(arg, l) (begin(arg) + (l)), end(arg)
#define _ALL_2(arg, l, r) (begin(arg) + (l)), (begin(arg) + (r) + 1)
#define ALL(...) _LOAD_4(__VA_ARGS__, _ALL_2, _ALL_1, _ALL_0)(__VA_ARGS__)

// :/

using namespace std;
using tp = long long int;
[[maybe_unused]] constexpr tp ZERO = 0, ONE = 1, INF = -1ull >> 2;
int WITHERING(int);
void MIST(int, char*[]);

template <typename _Ty> class _Lambda_t { _Ty lexp;public:template<typename __Ty
>_Lambda_t(__Ty&&lexp):lexp(static_cast<__Ty&&>(lexp)){}template<typename...__Ty
>decltype(auto)operator()(__Ty&&...args){return lexp(std::ref(*this),static_cast
<__Ty&&>(args)...); } }; template <typename _Ty> decltype (auto) lexp(_Ty&&l_exp
) {return _Lambda_t<typename std::decay<_Ty>::type>(static_cast<_Ty&&>(l_exp));}
struct SPLITMIX { static uint64_t splitmix(uint64_t x){x+=0x9e3779b97f4a7c15;x=(
x ^ (x >> 30)) * 0xbf58476d1ce4e5b9; x = (x ^ (x>>27))*0x94d049bb133111eb;return
x ^ (x >> 31); } size_t operator()(uint64_t x) const { static const uint64_t o =
chrono::steady_clock::now().time_since_epoch().count(); return splitmix(x+o);}};
template <typename _Ty> auto vcc(_Ty init, size_t s) { return std::vector<_Ty>(s
, init); } template <typename _Ty, typename... __Ty> auto vcc(_Ty init, size_t s
, __Ty... o) {auto ret=vcc(init,o...);return std::vector<decltype(ret)>(s,ret);}
template <typename _Ty1, typename _Ty2> bool ckmax(_Ty1& a, const _Ty2& b) { if(
a < b) { a = b; return true; } return false; } template <typename _Ty1, typename
_Ty2> bool ckmin(_Ty1& a, const _Ty2& b){if(b<a){a=b;return true;}return false;}
void RAW(char&x){if(__FREAD__!=0){static char buf[__FREAD__];static char*s=buf,*
e=buf;if(s==e){s=buf;e=buf+fread(buf,1,__FREAD__,stdin);if(s==e){x=EOF;return;}}
x = *s++; } else x = getchar(); } void bin(char& c){for(RAW(c);c==' '||c == '\n'
|| c == '\r'; RAW(c)); } void bin(std::string& x) { char c; for(RAW(c);c==' '||c
== '\n' || c == '\r'; RAW(c)); x = c; for (RAW(c); c!=' '&&c!='\n'&&c!='\r';RAW(
c)) x.push_back(c); } template <typename Ty> void bin(Ty& x) { bool sign = false
;char c; for (RAW(c); c < '0' || c > '9'; RAW(c)) if (c == '-') sign = true; for
(x = 0; '0' <= c && c <= '9'; RAW(c)) x = x * 10 + (c & 15); if (sign) x = -x; }
template <typename...> using bin_void_t =void;template<typename T,typename=void>
struct bin_it :std::false_type{};template<typename T>struct bin_it<T,bin_void_t<
typename std::iterator_traits<T>::iterator_category>>:std::true_type{};template<
typename T>struct bin_it<T*,void>:std::true_type{};template<typename T,typename=
typename std::enable_if<bin_it<T>::value>::type>void bin(T s,T e){while(s!=e)bin
(*s++);}template<typename...>struct bin_or:std::false_type{};template<typename T
, typename... O> struct bin_or<T,O...>:std::conditional<T::value,std::true_type,
bin_or<O...>>::type {}; template <typename... T>typename std::enable_if<!bin_or<
bin_it<typename std::decay<T>::type>...>::value, void>::type bin(T& ...x) {void(
(int[]) { 0, (bin(&x, &x + 1), 0) ... }); } tp bin() { tp x; bin(x); return x; }
int main(int argc, char* argv[]) { int t = 0, _t = 1; if(MTS&&!SPC_MTS) bin(_t);
MIST(argc, argv); while(t<_t||SPC_MTS){if(WITHERING(++t)!=0)return 0;}return 0;}
#ifdef XCODE
#define bg(...){cout<<"["<<__LINE__<<'@'<<++_LT[__LINE__]<<':';BG(__VA_ARGS__);}
size_t _LT[21777]; template<typename _Type>void BG(const _Type&_cur){cout<<' '<<
_cur << ']' <<" <<:"<<std::endl;}template<typename _Type,typename... _Other>void
BG(const _Type& _cur, const _Other& ..._other) {cout<< ' '<<_cur;BG(_other...);}
#else
#define bg(...)
#endif

// :/

namespace lib {  // LIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIBLIB
class Random{mt19937_64 rd;public:Random(unsigned long long seed) {rd=mt19937_64
(seed); } long long operator()(long long l, long long r) { return l + rd() % (r-
l + 1); } } rng(reinterpret_cast<unsigned long long>(new char) * time(nullptr));
}  // LIB::RANDOM LIB::RANDOM LIB::RANDOM LIB::RANDOM LIB::RANDOM LIB::RANDOM LI

// :/

struct STRUGGLE {
   STRUGGLE() {
      if (strlen(__FIN__)) freopen(__FIN__, "r", stdin);
      if (strlen(__FOUT__)) freopen(__FOUT__, "w", stdout);
   }
   
   ~STRUGGLE() {
   }
} STRUGGLE;

int WITHERING([[maybe_unused]] int TEST_NUMBER) {
   tp n; bin(n);
   vector<pair<tp, tp>> a(n);
   for (auto& [x, y] : a) bin(x, y);
   vector<pair<tp, tp>> p { make_pair(ZERO, ZERO) };
   tp tar = 0;
   for (tp i = 0; i < n; ++i) {
      auto [x, y] = a[i];
      while (p.size() >= 2 && (x < p[p.size() - 2].first || y < p[p.size() - 2].second)) {
         p.pop_back();
      }
      if (x >= p.back().first && y >= p.back().second) {
         tar += x - p.back().first;
         tar += y - p.back().second;
         p.emplace_back(x, y);
         if (p.size() >= 2 && p.back() == p[p.size() - 2]) p.pop_back();
         continue;
      }
      if (x <= p.back().first && y <= p.back().second) {
         p.back() = make_pair(x, y);
         if (p.size() >= 2 && p.back() == p[p.size() - 2]) p.pop_back();
         continue;
      }
      if (y <= p.back().second) {
         p.back().second = y;
         tar += x - p.back().first;
         p.emplace_back(x, y);
         if (p.size() >= 2 && p.back() == p[p.size() - 2]) p.pop_back();
         continue;
      }
      if (x <= p.back().first) {
         p.back().first = x;
         tar += y - p.back().second;
         p.emplace_back(x, y);
         if (p.size() >= 2 && p.back() == p[p.size() - 2]) p.pop_back();
         continue;
      }
      throw -1;
   }
   cout << tar << '\n';
   return 0;
}

void MIST([[maybe_unused]] int argc, [[maybe_unused]] char* argv[]) {
}

// :\ */