Compilare: user.cpp: In function ‘int main()’: user.cpp:37:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i <= elr.size(); ++i) ^ user.cpp:39:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < elr.size(); ++i) ^ user.cpp:45:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; (1<<i) - 1 <= elr.size(); ++i) ^ user.cpp:46:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j + (1<<i) - 1 <= elr.size(); ++j) ^