/*
For subtask 3, consider, for each rail, the prefix it can reach
4 2 1 0 -> doesn't work
3 1 1 1
4 2 2 0 -> works
3 2 1 1
4 3 1 0 -> works
4 2 1 1 -> doesn't work
2 2 4 0 -> doesn't work
The cost of a placement is.. hmm
max(t[i] - s[i + 1], 0) + max(t[i - 1] - s[i], 0) -> if separated more than two apart
t[i] t[i + 1] t[i + 2] t[i + 3]
s[i] s[i + 1] s[i + 2] s[i + 3]
c = max(t[i] - s[i + 1], 0) + max(t[i + 1] - s[i + 2], 0) + max(t[i + 2] - s[i + 3], 0)
c' = max(t[i] - s[i + 2], 0) + max(t[i + 2] - s[i + 1], 0) + max(t[i + 1] - s[i + 3], 0)
*/
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pi;
typedef pair<ll, ll> pll;
typedef vector<pi> vpi;
typedef vector<pll> vpll;
typedef vector<vpi> vvpi;
typedef vector<vpll> vvpll;
typedef vector<bool> vb;
#define IOS ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
#define L(varll, mn, mx) for(ll varll = (mn); varll < (mx); varll++)
#define LR(varll, mx, mn) for(ll varll = (mx); varll > (mn); varll--)
#define LI(vari, mn, mx) for(int vari = (mn); vari < (mx); vari++)
#define LIR(vari, mx, mn) for(int vari = (mx); vari > (mn); vari--)
#define INPV(varvec) for(auto& varveci : (varvec)) cin >> varveci
#define fi first
#define se second
#define pb push_back
#define INF(type) numeric_limits<type>::max()
#define NINF(type) numeric_limits<type>::min()
#define TCASES int t; cin >> t; while(t--)
ll plan_roller_coaster(vi s, vi t) {
ll n = s.size();
// Construct DP table
reverse(s.begin(), s.end()); // Lol thanks for the idea StackOverflow HAHAH
reverse(t.begin(), t.end());
s.pb(0);
t.pb(0);
reverse(s.begin(), s.end()); // Conjugation is crazy
reverse(t.begin(), t.end());
s.pb(INF(int));
t.pb(INF(int));
// It's time to bubble sort
LI(i, 0, n) {
LI(j, 0, n - 1) {
/*
c = max(t[i] - s[i + 1], 0) + max(t[i + 1] - s[i + 2], 0) + max(t[i + 2] - s[i + 3], 0)
c' = max(t[i] - s[i + 2], 0) + max(t[i + 2] - s[i + 1], 0) + max(t[i + 1] - s[i + 3], 0)
*/
int c = max(t[j] - s[j + 1], 0) + max(t[j + 1] - s[j + 2], 0) + max(t[j + 2] - s[j + 3], 0);
int cpr = max(t[j] - s[j + 2], 0) + max(t[j + 2] - s[j + 1], 0) + max(t[j + 1] - s[j + 3], 0);
if(cpr < c) {
swap(t[j + 1], t[j + 2]);
swap(s[j + 1], s[j + 2]);
}
}
}
ll ans = 0ll;
LI(i, 0, n + 1) {
ans = ans + max((ll)(t[i]) - (ll)(s[i + 1]), 0ll);
}
return ans;
}
#ifdef DEBUG
int main() {
int n;
cin >> n;
vi s(n, 0);
vi t(n, 0);
LI(i, 0, n) {
cin >> s[i] >> t[i];
}
cout << plan_roller_coaster(s, t) << endl;
}
#endif
