Compilare: user.cpp: In function ‘int main()’: user.cpp:13:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);i++) ~^~~~~~~~~~ user.cpp:15:21: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(s[i]>='a'&&s[i]<='z'||s[i]>='A'&&s[i]<='Z') ~~~~~~~~~^~~~~~~~~~~