Compilare: user.cpp: In function ‘bool check(int)’: user.cpp:168:9: warning: unused variable ‘sz’ [-Wunused-variable] int sz = 0; ^ user.cpp: In function ‘std::pair<int, int> lower(Treap*, int)’: user.cpp:149:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘char nextch()’: user.cpp:14:34: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf, 1, MAXBUF, fi); ^