Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:51:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v[0].size(); ++i) ^ user.cpp:59:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v[i].size(); ++j) ^ user.cpp:31:31: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d %d", &N, &M); ^ user.cpp:35:49: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d %d %d %d", &x, &y, &s, &g); ^