#include <bits/stdc++.h>

#define N 1000005

inline int R() {
    int x=0; bool f=0; char c=getchar();
    while (!isdigit(c)) f|=(c=='-'),c=getchar();
    while (isdigit(c)) x=x*10+c-'0',c=getchar();
    return f?-x:x;
}

template<typename T>
void W(T x,char Extra=0) {
    if (x<0) putchar('-'),x=-x; if (x>9) W(x/10);
    putchar(x%10+'0'); if (Extra) putchar(Extra);
}

using namespace std;
int n,a[N],b[N];

bool check(double mid) {
    double l=1e-7,r=1e9;
    for (int i=1;i<=n;i++) {
        double A=b[i],B=a[i]+b[i]-mid,C=a[i];
        if (B*B-4*A*C<0) return 0;
        auto tmp=sqrt(B*B-4*A*C);
        l=max(l,(-B-tmp)/(2*A)),r=min(r,(-B+tmp)/(2*A));
        if (l>r) return 0;
    }
    return l<=r;
}

int main() {
    n=R();
    for (int i=1;i<=n;i++) a[i]=R(),b[i]=R();
    double l=1,r=1e9,res=0;
    while (r-l>=1e-5) {
        double mid=(l+r)/2;
        if (check(mid)) r=mid,res=mid;
        else l=mid;
    }
    printf("%.4lf\n",res);
    return 0;
}