Compilare: main.cpp: In function 'int main()': main.cpp:21:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<s.size();i++) ~^~~~~~~~~ main.cpp:24:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<s.size() && s[i]>='0' && s[i]<='9') ~^~~~~~~~~