Compilare: user.cpp: In function ‘int main()’: user.cpp:121:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int l = 0; l < fr[k].size(); l++) ^ user.cpp:127:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int l = 0; l < Q[k].size(); l++) ^ user.cpp: In function ‘char read_chr()’: user.cpp:14:42: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf_in, 1, buf_size, stdin); ^ user.cpp: In function ‘int main()’: user.cpp:96:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("qxy.in", "r", stdin); ^ user.cpp:97:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("qxy.out", "w", stdout); ^