Compilare: main.cpp: In function 'int main()': main.cpp:56:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0 ; i < s.size() ; i++) ~~^~~~~~~~~~ main.cpp:59:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < s.size() && s[i] >= '0' && s[i] <= '9') ~~^~~~~~~~~~ main.cpp:88:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0 ; i < s.size() ; i++) ~~^~~~~~~~~~ main.cpp:91:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < s.size() && s[i] >= '0' && s[i] <= '9') ~~^~~~~~~~~~