Compilare: user.cpp: In function ‘int main()’: user.cpp:12:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^ user.cpp:28:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ^ user.cpp:33:58: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(!(s[i]-'a'>=0 && s[i]-'a'<=25) && i<s.size())i++; ^ user.cpp:34:55: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i]-'a'>=0 && s[i]-'a'<=25 && i<s.size()) ^ user.cpp:42:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i]==' ' && i<s.size())i++; ^ user.cpp:43:54: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i]-'0'>=0 && s[i]-'0'<=9 && i<s.size()) ^ user.cpp:49:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i!=s.size()) ^