Compilare: user.cpp: In function ‘int back(int)’: user.cpp:19:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (v[num[i]][p].size()<=cnt[num[i]]) ^ user.cpp:30:14: warning: no return statement in function returning non-void [-Wreturn-type] num[lvl]=0;}}} ^ user.cpp: In function ‘int main()’: user.cpp:32:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tricouri.in","r",stdin); ^ user.cpp:33:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tricouri.out","w",stdout); ^ user.cpp:35:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:37:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x[i]); ^ user.cpp:44:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&k,&p); ^