Compilare: main.cpp: In function 'int main()': main.cpp:35:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.length();i++){ ~^~~~~~~~~~~ main.cpp:40:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < s.length() && isdigit(s[i])){ ~~^~~~~~~~~~~~ main.cpp: In function 'long long int operatii(long long int, long long int, char)': main.cpp:25:1: warning: control reaches end of non-void function [-Wreturn-type] } ^