Compilare: user.cpp: In function ‘int main()’: user.cpp:53:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[j] < '0' || s[j] > '9') && j < s.size()) j++; ^ user.cpp:57:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[j] >= '0' && s[j] <= '9') && j < s.size()) ^ user.cpp:70:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[i] < '0' || s[i] > '9') && i < s.size()) i++; ^ user.cpp:74:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[i] >= '0' && s[i] <= '9') && i < s.size()) ^ user.cpp:81:61: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[i] < '0' || s[i] > '9') && i < s.size()) i++; ^ user.cpp:85:63: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while( (s[i] >= '0' && s[i] <= '9') && i < s.size()) ^