Compilare: main.cpp: In function 'int main()': main.cpp:30:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i <= n; v[i] = i - 1, ++i); ~~^~~~ main.cpp:32:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i <= n / 2; ++i) ~~^~~~~~~~ main.cpp:34:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 2 * i; j <= n; v[j] -= v[i], j += i); ~~^~~~ main.cpp:36:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i <= n; sol += v[i++]); ~~^~~~