Compilare: user.cpp: In function ‘void dfs(int, int)’: user.cpp:17:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[k].size(); ++i) ^ user.cpp: In function ‘void solve(int, std::pair<int, int>)’: user.cpp:47:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[k].size(); ++i) ^ user.cpp:67:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[k].size(); ++i) ^