Compilare: main.cpp: In function 'bool litera(char)': main.cpp:10:22: warning: suggest parentheses around '&&' within '||' [-Wparentheses] return (x >= 'a' && x <= 'z' || x >= 'A' && x <= 'Z'); ~~~~~~~~~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:15:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<=sir.size(); ++i) ~^~~~~~~~~~~~