//~~~~~~~~~~~~~MJ®™~~~~~~~~~~~~~
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#define rep1(n) for(ll i=0; i<(ll)(n); ++i)
#define rep2(i,n) for(ll i=0; i<(ll)(n); ++i)
#define rep3(i,a,b) for(ll i=(ll)(a); i<(ll)(b); ++i)
#define rep4(i,a,b,c) for(ll i=(ll)(a); i<(ll)(b); i+=(c))
#define cut4(a,b,c,d,e,...) e
#define rep(...) cut4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)
#define per1(n) for(ll i=((ll)n)-1; i>=0; --i)
#define per2(i,n) for(ll i=((ll)n)-1; i>=0; --i)
#define per3(i,a,b) for(ll i=((ll)a)-1; i>=(ll)(b); --i)
#define per4(i,a,b,c) for(ll i=((ll)a)-1; i>=(ll)(b); i-=(c))
#define per(...) cut4(__VA_ARGS__,per4,per3,per2,per1)(__VA_ARGS__)
#define ll long long
#define ln cout<<endl
#define int long long
#define vv vector<vi>
#define vp vector<pi>
#define append push_back
#define all(x) (x).begin(),(x).end()
#define allr(x) (x).rbegin(),(x).rend()
#define vi vector<int>
#define ret(x) {cout<<x;return;}
#define ui map<int,int>
#define pi pair<int,int>
#define ff first
#define ss second
using namespace std;
const int INF = 1e18, MOD = 1e9+7, N = 2e5+7;
void solve()
{
int n, k, e, m, ans = 0;
cin >> n;
vi a(n);
vi b(n);
map<int,int> fro;
map<int,int> bac;
rep(n)
{
cin >> a[i] >> b[i];
if (a[i])
{
fro[i]+=a[i];
}
}
bac[-INF] = INF;
fro[INF] = INF;
int now;
int temp, temp2;
rep(n)
{
now = b[i];
temp = fro.begin() -> ff;
temp2 = bac.rbegin() -> ff;
while (now)
{
auto k = fro.begin();
auto l = bac.rbegin();
if (k->ff -i <= i - l->ff )
{
// ans+=k->ff - i;
// cout << k->ff << " " << k->ss << endl;
// cout << i-k->ff << endl;
if (k->ss <= now)
{
now-=k->ss;
ans += (k->ff - i)*k->ss;
// cout << k->ff << " " << k->ss << endl;
// cout << i-k->ff << endl;
fro.erase(k->ff);
}
else
{
fro[k->ff]-=now;
ans+= (k->ff - i)*now ;
// cout << k->ff << " " << k->ss << endl;
// cout << i-k->ff << endl;
now = 0;
}
}
else
{
if (l->ss <= now)
{
ans += (i - l->ff)*l->ss;
now-=l->ss;
// cout << l->ff << " " << l->ss << endl;
// cout << i-l->ff << endl;
bac.erase(l->ff);
}
else
{
bac[l->ff]-=now;
ans+= (i - l->ff)*now ;
// cout << l->ff << " " << l->ss << endl;
// cout << i-l->ff << endl;
now = 0;
}
}
// cout << i << " "<< ans <<" " << temp << " " <<temp2 << endl;
}
if (fro.find(i)!= fro.end())
{
bac[i]+=fro[i];
fro.erase(i);
}
// bac[i] = fro[i];
}
cout << ans;
// cout << a.size();
// for (auto i: a){cout << i << " ";}
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL); cout.tie(NULL);
int ans=1;
//cout<<setprecision(1000);
// cin>>ans;
rep(ans){
// cout << "Case #" << i+1 << ": ";
solve();ln;}}
