// g++ -std=c++11 a.cpp
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>	
#include<map>
#include<set>
#include<unordered_map>
#include<utility>
#include<cmath>
#include<random>
#include<cstring>
#include<queue>
#include<stack>
#include<bitset>
#include<cstdio>
#include<sstream>
#include<iomanip>
#include<assert.h>
#include<typeinfo>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define FOR(i,a) for(auto i:a)
#define pb push_back
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)
#define show1d(v) rep(_,v.size())cout<<" "<<v[_];cout<<endl;
#define show2d(v) rep(_,v.size()){rep(__,v[_].size())cout<<" "<<v[_][__];cout<<endl;}cout<<endl;
using namespace std;
//kaewasuretyuui
typedef long long ll;
#define int ll
typedef int Def;
typedef pair<Def,Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def,pii> pip;
typedef vector<pip>vip;
// #define mt make_tuple
// typedef tuple<int,int,int> tp;
// typedef vector<tp> vt;
template<typename A,typename B>bool cmin(A &a,const B &b){return a>b?(a=b,true):false;}
template<typename A,typename B>bool cmax(A &a,const B &b){return a<b?(a=b,true):false;}
//template<class C>constexpr int size(const C &c){return (int)c.size();}
//template<class T,size_t N> constexpr int size(const T (&xs)[N])noexcept{return (int)N;}
const double PI=acos(-1);
const double EPS=1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 1e18+10 : 1e9+10;
int dx[]={0,1,0,-1,1,1,-1,-1};
int dy[]={1,0,-1,0,1,-1,1,-1};//RDLU
signed main(){
	int n;
	while(cin>>n,n){
		vvi in(n,vi(2));
		rep(i,n)rep(j,2)cin>>in[i][j];
		sort(all(in));
		int tim=0;
		queue<pii>que[2];
		rep(i,n)que[0].push({in[i][0],i});
		while(!que[0].empty()||!que[1].empty()){
			tim=inf;
			rep(i,2)if(!que[i].empty()){
				int t=que[i].front().first;
				if(tim>t)tim=t;
			}
			rep(i,2){
				vp ne;
				while(!que[i].empty()&&que[i].front().first<=tim){
					ne.pb(que[i].front());
					que[i].pop();
				}
				rep(j,ne.size())rep(k,ne.size())
					if(in[ne[j].second][0]<in[ne[k].second][0])swap(ne[j],ne[k]);
				rep(j,ne.size()){
					pii p=ne[j];
					if(i){
						in[p.second][1]--;
						if(in[p.second][1])que[i^1].push({tim+in[p.second][0],p.second});
					}else que[i^1].push({tim+in[p.second][0],p.second});
				}
			}
		}
		cout<<tim<<endl;
	}
}







