#include<bits/stdc++.h>
#define r(i,n) for(int i=0;i<n;i++)
using namespace std;
int n;
double a[100001],q[100001];
int main(){
  cin>>n;
  r(i,n)cin>>a[i]>>q[i];
  double l=0,r=1e9+1;
  r(o,100){
    double mid=(l+r)/2,lm=0,rm=1e9+1;
    r(i,n){
      if(q[i]<mid)rm=-1;
      lm=max(lm,a[i]-sqrt(q[i]*q[i]-mid*mid));
      rm=min(rm,a[i]+sqrt(q[i]*q[i]-mid*mid));
    }
    if(lm<rm)l=mid;
    else r=mid;
  }
  printf("%.9f\n",l);
}