Problem p00745 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <valarray>
#include <vector>
using namespace std;
typedef long long int ll;
typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;

#define REP(i, x) for (int i = 0; i < (int)(x); i++)
#define REPS(i, x) for (int i = 1; i <= (int)(x); i++)
#define RREP(i, x) for (int i = ((int)(x)-1); i >= 0; i--)
#define RREPS(i, x) for (int i = ((int)(x)); i > 0; i--)
#define FOR(i, c)                                                              \
  for (__typeof((c).begin()) i = (c).begin(); i != (c).end(); i++)
#define RFOR(i, c)                                                             \
  for (__typeof((c).rbegin()) i = (c).rbegin(); i != (c).rend(); i++)
#define ALL(container) (container).begin(), (container).end()
#define RALL(container) (container).rbegin(), (container).rend()
#define SZ(container) ((int)container.size())
#define mp(a, b) make_pair(a, b)
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &t) {
  os << "[";
  FOR(it, t) {
    if (it != t.begin())
      os << ",";
    os << *it;
  }
  os << "]";
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &t) {
  os << "{";
  FOR(it, t) {
    if (it != t.begin())
      os << ",";
    os << *it;
  }
  os << "}";
  return os;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &t) {
  return os << "(" << t.first << "," << t.second << ")";
}
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}

namespace geom {
#define X real()
#define Y imag()
#define at(i) ((*this)[i])
#define SELF (*this)
enum { TRUE = 1, FALSE = 0, BORDER = -1 };
typedef int BOOL;
typedef long double R;
const R INF = 1e8;
R EPS = 1e-8;
const R PI = 3.1415926535897932384626;
inline int sig(const R &x) { return (abs(x) < EPS ? 0 : x > 0 ? 1 : -1); }
inline BOOL less(const R &x, const R &y) { return sig(x - y) ? x < y : BORDER; }
typedef complex<R> P;
inline R norm(const P &p) { return p.X * p.X + p.Y * p.Y; }
inline R inp(const P &a, const P &b) { return (conj(a) * b).X; }
inline R outp(const P &a, const P &b) { return (conj(a) * b).Y; }
inline P unit(const P &p) { return p / abs(p); }
inline P proj(const P &s, const P &t) { return t * inp(s, t) / norm(t); }
inline int ccw(const P &s, const P &t, const P &p, int adv = 0) {
  int res = sig(outp(t - s, p - s));
  if (res || !adv)
    return res;
  if (sig(inp(t - s, p - s)) < 0)
    return -2; // p-s-t
  if (sig(inp(s - t, p - t)) < 0)
    return 2; // s-t-p
  return 0;   // s-p-t
}

struct L : public vector<P> { // line
  L(const P &p1, const P &p2) {
    this->push_back(p1);
    this->push_back(p2);
  }
  L() {}
  P dir() const { return at(1) - at(0); }
  BOOL online(const P &p) const { return !sig(outp(p - at(0), dir())); }
};
struct S : public L { // segment
  S(const P &p1, const P &p2) : L(p1, p2) {}
  S() {}
  BOOL online(const P &p) const {
    if (!sig(norm(p - at(0))) || !sig(norm(p - at(1))))
      return BORDER;
    // 座標の二乗とEPSの差が大きすぎないように注意
    return !sig(outp(p - at(0), dir())) && inp(p - at(0), dir()) > EPS &&
           inp(p - at(1), -dir()) > -EPS;
    // return !sig(abs(at(0)-p) + abs(at(1) - p) - abs(at(0) - at(1)));
  }
};
struct C : public P {
  C() {}
  C(const P &p, const R r) : P(p), r(r) {}
  R r;
  BOOL inside(const P &p) const { return less(norm(p - SELF), r * r); }
};
struct F : public C {
  R s, t;
  F(const C &c, R ss, R tt) : C(c), s(ss), t(tt) {
    if (PI < s)
      s -= 2 * PI;
    if (PI < t)
      t -= 2 * PI;
  }
  BOOL inside(const P &p) const {
    P v = p - SELF;
    if (!sig(norm(v)))
      return BORDER;
    R a = arg(v);
    if (t < s) {
      if ((!less(s, a) && !less(a, t)) || !less(norm(v), r * r))
        return FALSE;
      return less(s, a) | less(a, t) | less(norm(v), r * r);
    } else {
      if (!less(s, a) || !less(a, t) || !less(norm(v), r * r))
        return FALSE;
      return less(s, a) | less(a, t) | less(norm(v), r * r);
    }
  }
};
P crosspoint(const L &l, const L &m);
struct G : public vector<P> {
  G(size_type size = 0) : vector(size) {}
  S edge(int i) const { return S(at(i), at(i + 1 == size() ? 0 : i + 1)); }
  BOOL contains(const P &p) const {
    R sum = .0;
    REP(i, size()) {
      if (S(at(i), at((i + 1) % size())).online(p))
        return BORDER; // online
      sum += arg((at(i) - p) / (at((i + 1) % size()) - p));
    }
    return !!sig(sum);
  }
  R area() const {
    R sum = 0;
    REP(i, size()) sum += outp(at(i), at((i + 1) % size()));
    return abs(sum / 2.);
  }
  P gp() const {
    P r(.0, .0);
    REP(i, size()) {
      const S &s = edge(i);
      r += (s[0] + s[1]) * outp(s[0], s[1]);
    }
    return r / (6 * area());
  }
  G convex_hull(bool online = false) {
    if (size() < 2)
      return *this;
    sort(ALL(*this));
    G r;
    r.resize((int)size() * 2);
    int k = 0;
    for (int i = 0; i < size(); r[k++] = at(i++))
      while (k > 1 && ccw(r[k - 2], r[k - 1], at(i)) < 1 - online)
        k--;
    int t = k;
    for (int i = (int)size() - 1; i >= 0; r[k++] = at(i--))
      while (k > t && ccw(r[k - 2], r[k - 1], at(i)) < 1 - online)
        k--;
    r.resize(k - 1);
    return r;
  }
  G cut(const L &l) const {
    G g;
    REP(i, size()) {
      const S &s = edge(i);
      if (ccw(l[0], l[1], s[0], 0) >= 0)
        g.push_back(s[0]);
      if (ccw(l[0], l[1], s[0], 0) * ccw(l[0], l[1], s[1], 0) < 0)
        g.push_back(crosspoint(s, l));
    }
    return g;
  }
  G Voronoi(const vector<P> &p, const int t) const {
    G g = *this;
    REP(i, p.size()) if (i != t) {
      const P m = (p[t] + p[i]) * (R)0.5;
      g = g.cut(L(m, m + (p[i] - p[t]) * P(0, 1)));
    }
    return g;
  }
};

inline P proj(const P &s, const L &t) {
  return t[0] + proj(s - t[0], t[1] - t[0]);
}
inline P reflect(const P &s, const L &t) { return (R)2. * proj(s, t) - s; }
inline S reflect(const S &s, const L &t) {
  return S(reflect(s[0], t), reflect(s[1], t));
}
BOOL intersect(const S &s, const S &t) {
  const int p = ccw(t[0], t[1], s[0], 1) * ccw(t[0], t[1], s[1], 1);
  const int q = ccw(s[0], s[1], t[0], 1) * ccw(s[0], s[1], t[1], 1);
  return (p > 0 || q > 0) ? FALSE : (!p || !q) ? BORDER : TRUE;
}
BOOL intersect(const S &s, const L &l) {
  if (l.online(s[0]) || l.online(s[1]))
    return BORDER;
  return (sig(outp(l.dir(), s[0] - l[0])) * sig(outp(l.dir(), s[1] - l[0])) <=
          0);
}
R dist2(const L &l, const P &p) {
  return norm(outp(l.dir(), p - l[0])) / norm(l.dir());
}
R dist2(const S &s, const P &p) {
  if (inp(p - s[0], s.dir()) < EPS)
    return norm(p - s[0]);
  if (inp(p - s[1], -s.dir()) < EPS)
    return norm(p - s[1]);
  return dist2((const L &)s, p);
}
R dist2(const S &s, const L &l) {
  return intersect(s, l) ? .0 : min(dist2(l, s[0]), dist2(l, s[1]));
}
R dist2(const S &s, const S &t) {
  return intersect(s, t) ? .0
                         : min(min(dist2(s, t[0]), dist2(t, s[0])),
                               min(dist2(s, t[1]), dist2(t, s[1])));
}
template <class T>
R dist2(const G &g, const T &t) { // todo: 内部に完全に含まれる場合
  R res = INF;
  REP(i, g.size()) res = min(res, dist2(g.edge(i), t));
  return res;
}
template <class S, class T> R dist(const S &s, const T &t) {
  return sqrt(dist2(s, t));
}
inline BOOL intersect(const C &a, const C &b) {
  return less((a.r - b.r) * (a.r - b.r), norm(a - b)) +
         less(norm(a - b), (a.r + b.r) * (a.r + b.r)) - 1;
}
inline BOOL intersect(const C &c, const L &l) {
  return less(dist2(l, c), c.r * c.r);
}
inline BOOL intersect(const C &c, const S &s) {
  int d = less(dist2(s, c), c.r * c.r);
  if (d != TRUE)
    return d;
  int p = c.inside(s[0]), q = c.inside(s[1]);
  return (p < 0 || q < 0) ? BORDER : p & q;
}
inline P crosspoint(const L &l, const L &m) {
  R A = outp(l.dir(), m.dir()), B = outp(l.dir(), l[1] - m[0]);
  if (!sig(abs(A)) && !sig(abs(B)))
    return m[0]; // same line
  if (abs(A) < EPS)
    assert(false); // !!!PRECONDITION NOT SATISFIED!!!
  return m[0] + B / A * (m[1] - m[0]);
}

#undef SELF
#undef at
} // namespace geom

using namespace geom;

int f = 0;
namespace std {
bool operator<(const P &a, const P &b) {
  return sig(a.X - b.X) ? a.X < b.X : a.Y + EPS < b.Y;
}
bool operator==(const P &a, const P &b) { return abs(a - b) < EPS; }
istream &operator>>(istream &is, P &p) {
  R x, y;
  is >> x >> y;
  p = P(x, y);
  return is;
}
istream &operator>>(istream &is, L &l) {
  l.resize(2);
  return is >> l[0] >> l[1];
}
istream &operator>>(istream &is, C &c) { return is >> (P &)c >> c.r; }
const R B = 200;
const R Z = .5;
ostream &operator<<(ostream &os, const C &c) {
  return os << "circle(" << B + Z * (c.X) << ", " << 1000 - B - Z * (c.Y)
            << ", " << Z * (c.r) << ")";
}
ostream &operator<<(ostream &os, const P &p) { return os << C(p, 2. / Z); }
ostream &operator<<(ostream &os, const S &s) {
  return os << "line(" << B + Z * (s[0].X) << ", " << 1000 - B - Z * (s[0].Y)
            << ", " << B + Z * (s[1].X) << ", " << 1000 - B - Z * (s[1].Y)
            << ")";
}
ostream &operator<<(ostream &os, const G &g) {
  REP(i, g.size()) os << g.edge(i) << endl;
  return os;
}

} // namespace std

int n, m;

vi path(S root, const vector<P> &pin) {
  vi res;
  if (!sig(root.dir().X))
    return res;
  REPS(i, n) {
    P cp = crosspoint(root, L(pin[i], pin[i] + P(0, 1)));
    if (root.online(cp) == FALSE)
      continue;
    if (abs(root[0].X - cp.X) < EPS || abs(root[1].X - cp.X) < EPS)
      continue;
    res.push_back(pin[i].Y < cp.Y ? i : -i);
  }
  sort(ALL(res), [&](int i, int j) {
    return abs(root[0].X - pin[abs(i)].X) < abs(root[0].X - pin[abs(j)].X);
  });
  return res;
}

int main(int argc, char *argv[]) {
  ios::sync_with_stdio(false);
  int T = 1;
  while (cin >> m >> n, n) {
    vector<P> root(m), pin(n + 1);
    REP(i, m) {
      cin >> root[i];
      root[i] *= polar((R)1, (R)1);
    }
    pin[0] = root[0];
    REPS(i, n) {
      cin >> pin[i];
      pin[i] *= polar((R)1, (R)1);
    }
    sort(pin.begin() + 1, pin.end());
    pin.push_back(root.back());
    vector<int> st;
    st.push_back(0);
    REP(i, m - 1) {
      S s(root[i], root[i + 1]);
      vi isc = path(s, pin);
      FOR(it, isc) {
        if (st.back() == *it)
          st.pop_back();
        else
          st.push_back(*it);
      }
    }
    st.push_back(n + 1);

    vector<R> dp(st.size(), INF);
    vi prev(st.size());
    dp[0] = .0;
    int save = 0;
    REP(i, st.size()) {
      if (i && st[i] == -st[i - 1]) {
        save = i;
        dp[i] = dp[i - 1];
        prev[i] = prev[i - 1];
        continue;
      }
      for (int j = save; j < i; j++) {
        S r(pin[abs(st[j])], pin[abs(st[i])]);
        vi pt = path(r, pin);
        if ([&]() {
              for (int k = 1; k <= pt.size() && j + k < i; k++)
                if (pt[k - 1] != st[j + k])
                  return 0;
              return 1;
            }()) {
          if (chmin(dp[i], dp[j] + abs(r.dir()))) {
            prev[i] = j;
          }
        }
      }
    }
    printf("%.10f\n", (double)dp.back());
  }
  return 0;
}

Fixed submission:
#include <algorithm>
#include <assert.h>
#include <bitset>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <valarray>
#include <vector>
using namespace std;
typedef long long int ll;
typedef unsigned int uint;
typedef unsigned char uchar;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;

#define REP(i, x) for (int i = 0; i < (int)(x); i++)
#define REPS(i, x) for (int i = 1; i <= (int)(x); i++)
#define RREP(i, x) for (int i = ((int)(x)-1); i >= 0; i--)
#define RREPS(i, x) for (int i = ((int)(x)); i > 0; i--)
#define FOR(i, c)                                                              \
  for (__typeof((c).begin()) i = (c).begin(); i != (c).end(); i++)
#define RFOR(i, c)                                                             \
  for (__typeof((c).rbegin()) i = (c).rbegin(); i != (c).rend(); i++)
#define ALL(container) (container).begin(), (container).end()
#define RALL(container) (container).rbegin(), (container).rend()
#define SZ(container) ((int)container.size())
#define mp(a, b) make_pair(a, b)
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> ostream &operator<<(ostream &os, const vector<T> &t) {
  os << "[";
  FOR(it, t) {
    if (it != t.begin())
      os << ",";
    os << *it;
  }
  os << "]";
  return os;
}
template <class T> ostream &operator<<(ostream &os, const set<T> &t) {
  os << "{";
  FOR(it, t) {
    if (it != t.begin())
      os << ",";
    os << *it;
  }
  os << "}";
  return os;
}
template <class S, class T>
ostream &operator<<(ostream &os, const pair<S, T> &t) {
  return os << "(" << t.first << "," << t.second << ")";
}
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) {
  return pair<S, T>(s.first - t.first, s.second - t.second);
}

namespace geom {
#define X real()
#define Y imag()
#define at(i) ((*this)[i])
#define SELF (*this)
enum { TRUE = 1, FALSE = 0, BORDER = -1 };
typedef int BOOL;
typedef double R;
const R INF = 1e8;
R EPS = 1e-8;
const R PI = 3.1415926535897932384626;
inline int sig(const R &x) { return (abs(x) < EPS ? 0 : x > 0 ? 1 : -1); }
inline BOOL less(const R &x, const R &y) { return sig(x - y) ? x < y : BORDER; }
typedef complex<R> P;
inline R norm(const P &p) { return p.X * p.X + p.Y * p.Y; }
inline R inp(const P &a, const P &b) { return (conj(a) * b).X; }
inline R outp(const P &a, const P &b) { return (conj(a) * b).Y; }
inline P unit(const P &p) { return p / abs(p); }
inline P proj(const P &s, const P &t) { return t * inp(s, t) / norm(t); }
inline int ccw(const P &s, const P &t, const P &p, int adv = 0) {
  int res = sig(outp(t - s, p - s));
  if (res || !adv)
    return res;
  if (sig(inp(t - s, p - s)) < 0)
    return -2; // p-s-t
  if (sig(inp(s - t, p - t)) < 0)
    return 2; // s-t-p
  return 0;   // s-p-t
}

struct L : public vector<P> { // line
  L(const P &p1, const P &p2) {
    this->push_back(p1);
    this->push_back(p2);
  }
  L() {}
  P dir() const { return at(1) - at(0); }
  BOOL online(const P &p) const { return !sig(outp(p - at(0), dir())); }
};
struct S : public L { // segment
  S(const P &p1, const P &p2) : L(p1, p2) {}
  S() {}
  BOOL online(const P &p) const {
    if (!sig(norm(p - at(0))) || !sig(norm(p - at(1))))
      return BORDER;
    // 座標の二乗とEPSの差が大きすぎないように注意
    return !sig(outp(p - at(0), dir())) && inp(p - at(0), dir()) > EPS &&
           inp(p - at(1), -dir()) > -EPS;
    // return !sig(abs(at(0)-p) + abs(at(1) - p) - abs(at(0) - at(1)));
  }
};
struct C : public P {
  C() {}
  C(const P &p, const R r) : P(p), r(r) {}
  R r;
  BOOL inside(const P &p) const { return less(norm(p - SELF), r * r); }
};
struct F : public C {
  R s, t;
  F(const C &c, R ss, R tt) : C(c), s(ss), t(tt) {
    if (PI < s)
      s -= 2 * PI;
    if (PI < t)
      t -= 2 * PI;
  }
  BOOL inside(const P &p) const {
    P v = p - SELF;
    if (!sig(norm(v)))
      return BORDER;
    R a = arg(v);
    if (t < s) {
      if ((!less(s, a) && !less(a, t)) || !less(norm(v), r * r))
        return FALSE;
      return less(s, a) | less(a, t) | less(norm(v), r * r);
    } else {
      if (!less(s, a) || !less(a, t) || !less(norm(v), r * r))
        return FALSE;
      return less(s, a) | less(a, t) | less(norm(v), r * r);
    }
  }
};
P crosspoint(const L &l, const L &m);
struct G : public vector<P> {
  G(size_type size = 0) : vector(size) {}
  S edge(int i) const { return S(at(i), at(i + 1 == size() ? 0 : i + 1)); }
  BOOL contains(const P &p) const {
    R sum = .0;
    REP(i, size()) {
      if (S(at(i), at((i + 1) % size())).online(p))
        return BORDER; // online
      sum += arg((at(i) - p) / (at((i + 1) % size()) - p));
    }
    return !!sig(sum);
  }
  R area() const {
    R sum = 0;
    REP(i, size()) sum += outp(at(i), at((i + 1) % size()));
    return abs(sum / 2.);
  }
  P gp() const {
    P r(.0, .0);
    REP(i, size()) {
      const S &s = edge(i);
      r += (s[0] + s[1]) * outp(s[0], s[1]);
    }
    return r / (6 * area());
  }
  G convex_hull(bool online = false) {
    if (size() < 2)
      return *this;
    sort(ALL(*this));
    G r;
    r.resize((int)size() * 2);
    int k = 0;
    for (int i = 0; i < size(); r[k++] = at(i++))
      while (k > 1 && ccw(r[k - 2], r[k - 1], at(i)) < 1 - online)
        k--;
    int t = k;
    for (int i = (int)size() - 1; i >= 0; r[k++] = at(i--))
      while (k > t && ccw(r[k - 2], r[k - 1], at(i)) < 1 - online)
        k--;
    r.resize(k - 1);
    return r;
  }
  G cut(const L &l) const {
    G g;
    REP(i, size()) {
      const S &s = edge(i);
      if (ccw(l[0], l[1], s[0], 0) >= 0)
        g.push_back(s[0]);
      if (ccw(l[0], l[1], s[0], 0) * ccw(l[0], l[1], s[1], 0) < 0)
        g.push_back(crosspoint(s, l));
    }
    return g;
  }
  G Voronoi(const vector<P> &p, const int t) const {
    G g = *this;
    REP(i, p.size()) if (i != t) {
      const P m = (p[t] + p[i]) * (R)0.5;
      g = g.cut(L(m, m + (p[i] - p[t]) * P(0, 1)));
    }
    return g;
  }
};

inline P proj(const P &s, const L &t) {
  return t[0] + proj(s - t[0], t[1] - t[0]);
}
inline P reflect(const P &s, const L &t) { return (R)2. * proj(s, t) - s; }
inline S reflect(const S &s, const L &t) {
  return S(reflect(s[0], t), reflect(s[1], t));
}
BOOL intersect(const S &s, const S &t) {
  const int p = ccw(t[0], t[1], s[0], 1) * ccw(t[0], t[1], s[1], 1);
  const int q = ccw(s[0], s[1], t[0], 1) * ccw(s[0], s[1], t[1], 1);
  return (p > 0 || q > 0) ? FALSE : (!p || !q) ? BORDER : TRUE;
}
BOOL intersect(const S &s, const L &l) {
  if (l.online(s[0]) || l.online(s[1]))
    return BORDER;
  return (sig(outp(l.dir(), s[0] - l[0])) * sig(outp(l.dir(), s[1] - l[0])) <=
          0);
}
R dist2(const L &l, const P &p) {
  return norm(outp(l.dir(), p - l[0])) / norm(l.dir());
}
R dist2(const S &s, const P &p) {
  if (inp(p - s[0], s.dir()) < EPS)
    return norm(p - s[0]);
  if (inp(p - s[1], -s.dir()) < EPS)
    return norm(p - s[1]);
  return dist2((const L &)s, p);
}
R dist2(const S &s, const L &l) {
  return intersect(s, l) ? .0 : min(dist2(l, s[0]), dist2(l, s[1]));
}
R dist2(const S &s, const S &t) {
  return intersect(s, t) ? .0
                         : min(min(dist2(s, t[0]), dist2(t, s[0])),
                               min(dist2(s, t[1]), dist2(t, s[1])));
}
template <class T>
R dist2(const G &g, const T &t) { // todo: 内部に完全に含まれる場合
  R res = INF;
  REP(i, g.size()) res = min(res, dist2(g.edge(i), t));
  return res;
}
template <class S, class T> R dist(const S &s, const T &t) {
  return sqrt(dist2(s, t));
}
inline BOOL intersect(const C &a, const C &b) {
  return less((a.r - b.r) * (a.r - b.r), norm(a - b)) +
         less(norm(a - b), (a.r + b.r) * (a.r + b.r)) - 1;
}
inline BOOL intersect(const C &c, const L &l) {
  return less(dist2(l, c), c.r * c.r);
}
inline BOOL intersect(const C &c, const S &s) {
  int d = less(dist2(s, c), c.r * c.r);
  if (d != TRUE)
    return d;
  int p = c.inside(s[0]), q = c.inside(s[1]);
  return (p < 0 || q < 0) ? BORDER : p & q;
}
inline P crosspoint(const L &l, const L &m) {
  R A = outp(l.dir(), m.dir()), B = outp(l.dir(), l[1] - m[0]);
  if (!sig(abs(A)) && !sig(abs(B)))
    return m[0]; // same line
  if (abs(A) < EPS)
    assert(false); // !!!PRECONDITION NOT SATISFIED!!!
  return m[0] + B / A * (m[1] - m[0]);
}

#undef SELF
#undef at
} // namespace geom

using namespace geom;

int f = 0;
namespace std {
bool operator<(const P &a, const P &b) {
  return sig(a.X - b.X) ? a.X < b.X : a.Y + EPS < b.Y;
}
bool operator==(const P &a, const P &b) { return abs(a - b) < EPS; }
istream &operator>>(istream &is, P &p) {
  R x, y;
  is >> x >> y;
  p = P(x, y);
  return is;
}
istream &operator>>(istream &is, L &l) {
  l.resize(2);
  return is >> l[0] >> l[1];
}
istream &operator>>(istream &is, C &c) { return is >> (P &)c >> c.r; }
const R B = 200;
const R Z = .5;
ostream &operator<<(ostream &os, const C &c) {
  return os << "circle(" << B + Z * (c.X) << ", " << 1000 - B - Z * (c.Y)
            << ", " << Z * (c.r) << ")";
}
ostream &operator<<(ostream &os, const P &p) { return os << C(p, 2. / Z); }
ostream &operator<<(ostream &os, const S &s) {
  return os << "line(" << B + Z * (s[0].X) << ", " << 1000 - B - Z * (s[0].Y)
            << ", " << B + Z * (s[1].X) << ", " << 1000 - B - Z * (s[1].Y)
            << ")";
}
ostream &operator<<(ostream &os, const G &g) {
  REP(i, g.size()) os << g.edge(i) << endl;
  return os;
}

} // namespace std

int n, m;

vi path(S root, const vector<P> &pin) {
  vi res;
  if (!sig(root.dir().X))
    return res;
  REPS(i, n) {
    P cp = crosspoint(root, L(pin[i], pin[i] + P(0, 1)));
    if (root.online(cp) == FALSE)
      continue;
    if (abs(root[0].X - cp.X) < EPS || abs(root[1].X - cp.X) < EPS)
      continue;
    res.push_back(pin[i].Y < cp.Y ? i : -i);
  }
  sort(ALL(res), [&](int i, int j) {
    return abs(root[0].X - pin[abs(i)].X) < abs(root[0].X - pin[abs(j)].X);
  });
  return res;
}

int main(int argc, char *argv[]) {
  ios::sync_with_stdio(false);
  int T = 1;
  while (cin >> m >> n, n) {
    vector<P> root(m), pin(n + 1);
    REP(i, m) {
      cin >> root[i];
      root[i] *= polar((R)1, (R)1);
    }
    pin[0] = root[0];
    REPS(i, n) {
      cin >> pin[i];
      pin[i] *= polar((R)1, (R)1);
    }
    sort(pin.begin() + 1, pin.end());
    pin.push_back(root.back());
    vector<int> st;
    st.push_back(0);
    REP(i, m - 1) {
      S s(root[i], root[i + 1]);
      vi isc = path(s, pin);
      FOR(it, isc) {
        if (st.back() == *it)
          st.pop_back();
        else
          st.push_back(*it);
      }
    }
    st.push_back(n + 1);

    vector<R> dp(st.size(), INF);
    vi prev(st.size());
    dp[0] = .0;
    int save = 0;
    REP(i, st.size()) {
      if (i && st[i] == -st[i - 1]) {
        save = i;
        dp[i] = dp[i - 1];
        prev[i] = prev[i - 1];
        continue;
      }
      for (int j = save; j < i; j++) {
        S r(pin[abs(st[j])], pin[abs(st[i])]);
        vi pt = path(r, pin);
        if ([&]() {
              for (int k = 1; k <= pt.size() && j + k < i; k++)
                if (pt[k - 1] != st[j + k])
                  return 0;
              return 1;
            }()) {
          if (chmin(dp[i], dp[j] + abs(r.dir()))) {
            prev[i] = j;
          }
        }
      }
    }
    printf("%.10f\n", (double)dp.back());
  }
  return 0;
}