Compilare: user.cpp: In function ‘void del(int, int)’: user.cpp:30:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a[x].size(); i++) ^ user.cpp: In function ‘std::vector<int> eul(int)’: user.cpp:56:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<y.size(); i++) ^ user.cpp: In function ‘void write()’: user.cpp:65:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<x.size(); i++) ^ user.cpp: At global scope: user.cpp:69:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^ user.cpp: In function ‘int main()’: user.cpp:72:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=1; i<a.size(); i++) ^