Compilare: user.cpp: In function ‘int main()’: user.cpp:41:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v[0].size(); i++) ^ user.cpp:59:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < v[top.b].size(); j++) ^ user.cpp:29:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.in", "r", stdin); ^ user.cpp:30:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.out", "w", stdout); ^ user.cpp:31:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:35:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &a, &b, &c); ^