Compilare: user.cpp: In function ‘int main()’: user.cpp:19:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++){ ^ user.cpp:20:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(i%2==0) ^ user.cpp:25:11: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(i%2!=0) ^