#include<bits/stdc++.h>
using namespace std;
#define INIT ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount
#define int ll
int t, n, m, k, a[300010], l, r;
int b[100010];
int q=1000000000;
int32_t main(){
INIT
cin>>n;
for(int i=1; i<=n; i++){
long double d, c; cin>>c>>d;
a[i]=c*q;
if( (a[i]%(q/10000))>0 ){
a[i]=a[i]-(a[i]%(q/10000))+(q/10000);
}
b[i]=d*q;
if( (b[i]%(q/10000))>0 ){
b[i]=b[i]-(b[i]%(q/10000))+(q/10000);
}
}
sort(b+1, b+1+n);
sort(a+1, a+1+n);
int j=0;
int s1=0, s2=0;
int res=0;
for(int i=1; i<=n; i++){
s1+=a[n-i+1];
res=max(res, min(s1,s2)-(i+j)*q);
while( (s2<s1) && (j<n) ){
res=max(res, min(s1, s2)-(i+j)*q);
j++;
s2+=b[n-j+1];
res=max(res, min(s1,s2)-(i+j)*q);
}
res=max(res, min(s1,s2)-(i+j)*q);
}
double a=res, b=q;
cout<<fixed<<setprecision(4)<<(a/b);
return 0;
}
