Compilare: main.cpp: In function 'void back_track(long long int, long long int, long long int, long long int)': main.cpp:26:7: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos>=d.size()){return;} ~~~^~~~~~~~~~ main.cpp: In function 'int32_t main()': main.cpp:52:57: warning: unused variable 'm' [-Wunused-variable] int l=1, r=((int)(1000*1000)*(1000*1000)*(1000*1000) ), m=(l+r)/2; ^