#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define int long long
#define ll long long
#define pb push_back
#define fi first
#define se second
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define ld long double
using namespace std;
typedef pair<int,int> pii;
typedef pair<char,char> pcc;
typedef pair<int,pii> ipii;
typedef pair<pii,pii> ipiii;
const int MAXN = 1e6+10;
const int MAXA = 1e6;
const int INF = 1e18+10;
const int MOD = 1e9+7;
const int LOG = 32;
const ld EPS = 1e-12;
int n, ans;
priority_queue <int, vector<int>, greater<int>> pq;
signed main(){
// ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n;
vector<pii> vec;
for(int i=1; i<=n; i++){
int x, y; cin>>x>>y; vec.pb({x,y});
}
sort(vec.begin(), vec.end());
int las = 0;
for(auto [x,y] : vec){
for(int i=las+1; i<=x; i++) pq.push(0);
vector <int> te;
for(int i=1; i<=y; i++){
int mn = pq.top(); te.pb(mn+1); pq.pop();
ans += mn;
}
for(auto in : te) pq.push(in);
las = x;
}
cout << ans << '\n';
}
