Compilare: main.cpp: In function 'long long int solve(int, int)': main.cpp:32:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(idx == factors.size()) ~~~~^~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:54:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < factors.size() ; ++i) ~~^~~~~~~~~~~~~~~~ main.cpp:61:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = last ; i < factors.size() ; ++i) ~~^~~~~~~~~~~~~~~~