In file included from /in/driver/main.cpp:1:0:
/in/shortestP2P.hpp: In member function 'bool ShortestP2P::circling_check(int, std::vector<int>&, std::vector<bool>&)':
/in/shortestP2P.hpp:285:39: error: conversion to 'int' from 'std::vector<int>::size_type {aka long unsigned int}' may alter its value [-Werror=conversion]
             for (int i = stack.size() - 1; i > 0; --i) {
                          ~~~~~~~~~~~~~^~~
cc1plus: all warnings being treated as errors