#import<algorithm>
enum{M=1<<17,B=20000};
int N,X[M],Y[M],I[M],P[M],A[M],i,j,k,l,m,n;
double z=1,t;
int R(int u){return P[u]==u?u:P[u]=R(P[u]);}
int D(int a,int b,int c){return(X[b]-X[a])*(Y[c]-Y[a])<=(Y[b]-Y[a])*(X[c]-X[a]);}
int main(){
	scanf("%d",&N);
	for(i=N;i--;I[i]=P[i]=i,A[i]=X[i]*B+Y[i])scanf("%d%d",X+i,Y+i);
	std::sort(I,I+N,[](int a,int b){return A[a]<A[b];});
	for(i=11;i--;)for(j=i?-11:0;++j<11;)if(i*i+j*j<101){
		for(k=l=0;l<N;m<0?++l:++k){
			(m=A[I[l]]-A[I[k]]-i*B-j)||(P[R(I[l])]=R(I[k]));
		}
	}
	std::sort(I,I+N,[](int a,int b){m=R(a)-R(b);return m?m<0:A[a]<A[b];});
	for(i=j=0;i<N;i=j){
		n=0;
		for(;j<N&&R(I[i])==R(I[j]);A[++n]=I[j++]){
			for(;n>1&&D(A[n-1],A[n],I[j]);--n);
		}
		m=n;
		for(k=j;k-->i;A[++n]=I[k]){
			for(;n>m&&D(A[n-1],A[n],I[k]);--n);
		}
		for(k=n;k;--k)for(l=n;l;--l){
			t=2+hypot(X[A[k]]-X[A[l]],Y[A[k]]-Y[A[l]]);
			z=z>t?z:t;
		}
	}
	printf("%.9f\n",z);
}