Compilare: main.cpp: In function 'std::__cxx11::string getpref(int, int)': main.cpp:71:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int dr=0;dr<s[j].size();dr++) ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:103:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<s[i].size();j++) ~^~~~~~~~~~~~ main.cpp:120:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:121:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<s[i].size();j++) ~^~~~~~~~~~~~ main.cpp:128:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:131:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<s.size();j++) ~^~~~~~~~~ main.cpp:175:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<order.size();i++) ~^~~~~~~~~~~~~ main.cpp: In function 'ull toint(char)': main.cpp:51:1: warning: control reaches end of non-void function [-Wreturn-type] } ^