Compilare: user.cpp: In function ‘int main()’: user.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(l=0;l<v[i].size();l++) ~^~~~~~~~~~~~ user.cpp:16:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("blis.in","r",stdin); ^ user.cpp:17:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%s",&k,a+1); ^