Compilare: user.cpp: In function ‘void update()’: user.cpp:8:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(st.size() > nivel) ^ user.cpp: In function ‘int cb(int)’: user.cpp:21:42: warning: unused variable ‘ppos’ [-Wunused-variable] int st = 0 , dr = ap[x].size() - 1 , ppos = ap[x][0]; ^ user.cpp: In function ‘int main()’: user.cpp:38:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.in","r",stdin); ^ user.cpp:39:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.out","w",stdout); ^ user.cpp:40:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (scanf("%d", &Q); Q; --Q) ^ user.cpp:43:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n", &instr, &x); ^