func_code_string: #include <bits/stdc++.h>   using namespace std;   string convertTostr(int x) {     stringstream ss;     ss << x;     string st;     st = ss.str();     return st;   }   unsigned long long convertToint(string y) {     unsigned long long num;     stringstream ss(y);     ss >> num;     return num;   }   unsigned long long fpow(unsigned long long b, unsigned long long p,                           unsigned long long m) {     if (p == 0) return 1;     if (p == 1) return b % m;     unsigned long long res = fpow(b, p / 2, m) % m;     res = (res * res) % m;     if (p % 2 != 0) res = (res * (b % m)) % m;     return res;   }   int main() {     std::cin.tie(0);     std::ios::sync_with_stdio(false);     int n;     cin >> n;     vector<pair<int, int> > vec;     int x, y;     for (int i = 0; i < n; i++) {       cin >> x >> y;       vec.push_back(make_pair(x, y));     }     int cnt = 0;     for (int i = 0; i < n - 2; i++) {       int curX = vec[i].first, curY = vec[i].second;       int nX = vec[i + 1].first, nY = vec[i + 1].second;       int aX = vec[i + 2].first, aY = vec[i + 2].second;       if ((nX > curX && aY > nY) || (nX < curX && aY < nY) ||           (nY > curY && aX < nX) || (nY < curY && aX > nX))         cnt++;     }     cout << cnt;     return 0;   }   