//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <queue>

using namespace std;

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define FF first
#define SS second

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);
const int INF = 1e9;
int N;

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  while(cin>>N,N){
	VI T(N);
	vector<pair<PII,int>> p1(N), p2;
	REP(i,N){
	  cin >> p1[i].FF.FF >> p1[i].FF.SS;
	  p1[i].SS = i;
	  T[i] = p1[i].FF.FF;
	}

	int ans = 0;
	while(!p1.empty() || !p2.empty()){
	  int mt = INF;
	  REP(i,SZ(p1)) mt = min(mt, p1[i].FF.FF);
	  REP(i,SZ(p2)) mt = min(mt, p2[i].FF.FF);

	  REP(i,SZ(p1)) p1[i].FF.FF -= mt;
	  REP(i,SZ(p2)) p2[i].FF.FF -= mt;
	  ans += mt;

	  int Mt = 0;
	  REP(i,SZ(p2)) Mt = max(Mt, p2[i].FF.FF);
	  REP(i,SZ(p1)){
		if(p1[i].FF.FF == 0){
		  int idx = p1[i].SS;
		  p2.PB(MP(MP(max(Mt,T[idx]), p1[i].FF.SS), idx));
		  p1.erase(p1.begin() + i);
		  --i;
		}
	  }

	  Mt = 0;
	  REP(i,SZ(p1)) Mt = max(Mt, p1[i].FF.FF);
	  REP(i,SZ(p2)){
		if(p2[i].FF.FF == 0){
		  if(p2[i].FF.SS > 1){
			int idx = p2[i].SS;
			p1.PB(MP(MP(max(Mt,T[idx]), p2[i].FF.SS-1), idx));
		  }
		  p2.erase(p2.begin() + i);
		  --i;
		}
	  }
	}
	cout << ans << endl;
  }

  return 0;
}