Compilare: main.cpp: In function 'int nr_nec()': main.cpp:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ind < s.size() and isdigit(s[ind])) ~~~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ind < s.size()) ~~~~^~~~~~~~~~ main.cpp:49:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(ind < s.size() and s[ind] == 'x') ~~~~^~~~~~~~~~ main.cpp:54:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(ind < s.size() and s[ind] == 'y') ~~~~^~~~~~~~~~ main.cpp:59:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(ind < s.size() and s[ind] == 'z') ~~~~^~~~~~~~~~ main.cpp:64:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if(ind < s.size() and s[ind] == 't') ~~~~^~~~~~~~~~