Compilare: user.cpp: In function ‘int main()’: user.cpp:50:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (_a = 0 ; _a < tmp.size() ; ++_a) ^ user.cpp:65:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (_a = 0 ; _a < tmp.size() ; ++_a) ^ user.cpp:91:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (_a = 0 ; _a < tmp.size() ; ++_a) ^ user.cpp:15:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("count.in" , "r" , stdin); ^ user.cpp:16:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("count.out" , "w" , stdout); ^ user.cpp:18:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &n); ^ user.cpp:19:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &m); ^ user.cpp:23:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &a); ^ user.cpp:24:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &b); ^