#include <cstdio>
#include <algorithm>

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,j) FOR(i,0,j)

typedef long long ll;

const int MAX_N = 1000;

class UnionFind{
public:
    UnionFind(int n){
        REP(i, n){
            par[i] = i;
            rank[i] = 0;
        }
    }
    int find(int x){
        if(x == par[x])return x;
        return par[x] = find(par[x]);
    }
    bool same(int x, int y){
        return find(x) == find(y);
    }
    void unite(int x, int y){
        x = find(x);
        y = find(y);
        if(x == y){return;}
        
        if(rank[x] > rank[y]){
            par[y] = x;
        }else{
            par[x] = y;
            if(rank[x] == rank[y]){rank[y]++;}
        }
    }
private:
    int rank[MAX_N], par[MAX_N];
};

UnionFind uf(1000);
double dist[1000][1000];

int main(){
    int N;
    scanf("%d", &N);

    if(N == 0){puts("1.0"); return 0;}

    ll X[1000], Y[1000];
    for(int i=0;i<N;i++){
        scanf("%lld %lld", X+i, Y+i);
    }

    for(int i=0;i<N;i++){
        for(int j=i+1;j<N;j++){
            ll dx = X[i] - X[j], dy = Y[i] - Y[j];
            ll d = dx * dx + dy * dy;
            if(d <= 100){
                uf.unite(i, j);
            }
            dist[i][j] = d;
        }
    }

    double res = 2.0;
    for(int i=0;i<N;i++){
        for(int j=i+1;j<N;j++){
            if(uf.same(i, j)){
                res = std::max(res, std::sqrt(dist[i][j]) + 2.0);
            }
        }
    }

    printf("%.10f\n", res);
}