Compilare: user.cpp: In function ‘int main()’: user.cpp:15:15: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') ^ user.cpp:18:18: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(!(d >= 'a' && d <= 'z' || d >= 'A' && d <= 'Z')) ^