Compilare: user.cpp: In function ‘int back(int)’: user.cpp:18:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (v[num[k]][p].size()<cnt2[num[k]]) ^ user.cpp:32:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (v[num[lvl]][p].size()<cnt2[num[lvl]]){ ^ user.cpp:37:13: warning: control reaches end of non-void function [-Wreturn-type] num[lvl]=0;}} ^ user.cpp: In function ‘int main()’: user.cpp:39:33: 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:40:35: 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:42:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:44:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x[i]); ^ user.cpp:51:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&k,&p); ^