Shared code

/* 777 */
#include <bits/stdc++.h>
using namespace std;

#define FAST_IO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

#define int long long
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define F first
#define S second
#define bitcount __builtin_popcount
#define bitcountll __builtin_popcountll

#define endl '\n'
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define ROF(i, a, b) for (int i = (a); i >= (b); --i)
#define EACH(x, a) for (auto& x : a)
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) (int)(x).size()

#define MAXV(x) *max_element(ALL(x))
#define MINV(x) *min_element(ALL(x))
#define SUMLL(x) accumulate(ALL(x),0LL)
#define SORTA(x) sort(ALL(x))
#define SORTFn(x,fn) sort(ALL(x),fn)
#define SORTD(x) sort(ALL(x),greater<int>())

#define debug(x) cerr << #x << " = " << x << endl;
#define PRINTVec(arr) {for(auto& x:arr)cout<<x<<" ";cout<<'\n';}
#define PRINTGrid(grid) {for(auto& row:grid)PRINTVec(row);}
template <typename... Args>
void PRINTArgs(Args&&... args){((cout<<args<< " "),...);cout<<endl;}

using VI = vector <int>;
using VII = vector <VI>;
using VIII = vector <VII>;
using PII = pair<int,int>;
using VPII = vector<PII>;

#define min_pq(T) priority_queue<T, vector<T>, greater<T>>
#define max_pq(T) priority_queue<T>

const int INF = 1e9;
const long long INF_LL = 1e18;
const int MOD = 1e9 + 7;
// const double PI = 3.14159265358979323846;

int add(int a, int b) { return (a + b) % MOD; }
int mul(int a, int b) { return (a * b) % MOD; }

void solve() {
    int n; cin >> n;
    min_pq(PII) minHeap;
    while (n--) {
        int lgt, stt;
        cin >> lgt >> stt;
        minHeap.push(MP(lgt, stt));
    }
    int t = 0, ans = 0;
    while(!minHeap.empty()) {
        auto [lgt, stt] = minHeap.top(); minHeap.pop();
        // cout << lgt << " " << stt << endl;
        t += lgt;
        ans += stt - t;
    }
    cout << ans << endl;
}

int32_t main() {
    FAST_IO
    int testcases = 1;
    // cin >> testcases;
    while (testcases--) solve();
    return 0;
}

// least burst time first, deadline doesn't matter for order