func_code_string: #include <bits/stdc++.h>   using namespace std;   const int inf = 2e9;   const long long Inf = 1e10;   const int N = 500005;   const double pi = acos(-1);   inline int IN() {     int x = 0;     int ch = 0, f = 0;     for (ch = getchar(); ch != -1 && (ch < 48 || ch > 57); ch = getchar())       f = (ch ==  - );     for (; ch >= 48 && ch <= 57; ch = getchar())       x = (x << 1) + (x << 3) + ch -  0 ;     return f ? (-x) : x;   }   int Pow(int x, int y, int p) {     int a = 1;     for (; y; y >>= 1, x = (long long)x * x % p)       if (y & 1) a = (long long)a * x % p;     return a;   }   int n, a;   double rad[N], dis[N], ang[N];   struct po {     double x, y;     po(double xv = 0, double yv = 0) { x = xv, y = yv; }     double norm() { return sqrt(x * x + y * y); }     po operator-(const po &a) const { return (po){x - a.x, y - a.y}; }   } b[N], P, Q;   pair<double, double> A[N];   int tot;   set<double> st;   int check(double rng) {     tot = 0;     st.clear();     for (int i = (int)(1); i <= (int)(n); i++) {       if (dis[i] >= rng + rad[i]) continue;       if (dis[i] <= fabs(rng - rad[i])) continue;       double bet =           (rng * rng + dis[i] * dis[i] - rad[i] * rad[i]) / (2 * rng * dis[i]);       double alp = ang[i];       bet = acos(bet);       double l = alp - bet, r = alp + bet;       if (l < 0) l += 2 * pi;       if (r < 0) r += 2 * pi;       if (l > r) swap(l, r);       A[++tot] = make_pair(l, r);     }     sort(A + 1, A + tot + 1);     for (int i = (int)(1); i <= (int)(tot); i++) {       auto t = st.lower_bound(A[i].first);       if (t != st.end() && *t < A[i].second) return 1;       st.insert(A[i].second);     }     return 0;   }   int main() {     scanf( %d%d , &n, &a);     P = po(a, 0);     Q = po(-a, 0);     for (int i = (int)(1); i <= (int)(n); i++) {       double x, y;       scanf( %lf%lf , &x, &y);       b[i] = po(x, y);       rad[i] = (b[i] - Q).norm();       b[i] = b[i] - P;       ang[i] = atan2(b[i].y, b[i].x);       dis[i] = b[i].norm();     }     double l = 0, r = 2 * a;     for (int i = (int)(1); i <= (int)(100); i++) {       double md = (l + r) / 2.;       if (check(md))         r = md;       else         l = md;     }     printf( %.10lf n , (l + r) / 2);     return 0;   }   