Compilare: user.cpp: In function ‘int main()’: user.cpp:31:39: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] while (x>='a' && x<='z' || x>='0' && x<='9') { ^ user.cpp:42:39: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] while (x>='A' && x<='Z' || x>='0' && x<='9') { ^