Compilare: main.cpp: In function 'int main()': main.cpp:83:24: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<std::set<int> >::size_type {aka long unsigned int}' [-Wformat=] printf("%d\n",C.size()); ^ main.cpp:84:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < C.size(); i++) { ~~^~~~~~~~~~ main.cpp:61:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in","r",stdin); ^ main.cpp:63:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out","w",stdout); ^ main.cpp:65:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&N,&M); ^ main.cpp:73:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&x,&y); ^