#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using vi = vector<ll>;
using vvi = vector<vi>;
using vc = vector<char>;
using vvc = vector<vc>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vs = vector<string>;
using pii = pair<ll, ll>;
using vpii = vector<pii>;
using vvpii = vector<vpii>;
using mint = modint998244353;
// using mint = modint1000000007;
#define endl '\n'
#define rep(i, a) for (ll i = 0; i < a; i++)
#define f(i, a, b) for (ll i = a; i < b; i++)
#define rf(i, a, b) for (ll i = a; i > b; i--)
#define all(x) (x).begin(), (x).end()
const ll INF = LLONG_MAX / 4;
vi dx = {1, 0, -1, 0, 1, 1, -1, -1};
vi dy = {0, 1, 0, -1, 1, -1, 1, -1};
void io_setup() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout << fixed << setprecision(16);
}

int main(void) {
    io_setup();
    int n;
    cin >> n;
    vi a(n), b(n);
    rep(i,n)cin >> a[i] >> b[i];
    // vector dp(2, vector<pii>(n, {0,0}));//dp[0][i].fisrt 合計ダメージ
    // dp[0][0] = {0,a[0]};
    // dp[1][0] = {b[0],0};
    // rep(i,n-1){
    // 	dp[0][i+1] = max(dp[0][i+1])
    // }
    int attack = 0;
    vi num(n);
    rf(i,n-1,-1){
    	if(a[i]*attack <= b[i]){//攻撃する
    		num[i] = 1;
    		attack++;
    	}else{
    		num[i]  =0;
    	}
    }
    attack = 0;
    ll ans = 0;
    rep(i,n){
    	if(num[i] == 1)ans += attack + b[i];
    	else attack += a[i];
    }
    cout << ans << endl;
}