Compilare: user.cpp: In function ‘void euler(int, int)’: user.cpp:23:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[x].size();++i) ^ user.cpp: In function ‘void df(int)’: user.cpp:56:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[x].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:109:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<d[i].size();++j) ^