#define __USE_MINGW_ANSI_STDIO 0
#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define int ll
using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define PB push_back

const ll LLINF = (1LL<<60);
const int INF = (1LL<<30);
const int MOD = 1000000007;

template <typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template <typename T> bool IN(T a, T b, T x) { return a<=x&&x<b; }
template<typename T> T ceil(T a, T b) { return a/b + !!(a%b); }
template<class S,class T>
ostream &operator <<(ostream& out,const pair<S,T>& a){
  out<<'('<<a.first<<','<<a.second<<')';
  return out;
}
template<class T>
ostream &operator <<(ostream& out,const vector<T>& a){
  out<<'[';
  REP(i, a.size()) {out<<a[i];if(i!=a.size()-1)out<<',';}
  out<<']';
  return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};

signed main(void)
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  while(true) {
    int n; cin >> n;
    if(!n) break;
    VI t(n), c(n);
    vector<PII> p(n);
    REP(i, n) {
      cin >> t[i] >> c[i];
      p[i] = {t[i], i};
    }
    sort(ALL(p));

    // (人i, 折り返すまでにかかる時間, 周回数)
    queue<VI> que[2];
    REP(i, n) que[0].push({p[i].second, p[i].first, 0});

    int ans = 0;
    while(que[0].size() || que[1].size()) {
      // curのqueueから取り出す
      int cur = 0;
      if(que[cur].empty()) cur ^= 1;
      else if(que[cur^1].size() && que[cur].front()[1] > que[cur^1].front()[1]) cur ^= 1;

      // next以下のものを取り出す
      VVI v;
      int next = que[cur].front()[1];
      while(que[cur].size() && que[cur].front()[1] <= next) {
        v.PB(que[cur].front());
        que[cur].pop();
      }
      // vの中身を速度順でソートする
      sort(ALL(v), [&](const VI&a, const VI&b){
        return t[a[0]] < t[b[0]];
      });
      // vの中身を次のqueueに移す
      REP(i, v.size()) {
        if(cur == 1) v[i][2]++;
        if(v[i][2] == c[v[i][0]]) ans = next;
        else que[cur^1].push({v[i][0], next+t[v[i][0]], v[i][2]});
      }
    }
    cout << ans << endl;
  }

  return 0;
}

