Compilare: user.cpp: In function ‘int main()’: user.cpp:8:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= n; phi[i++] = i - 1); ^ user.cpp:8:41: warning: operation on ‘i’ may be undefined [-Wsequence-point] for (int i = 1; i <= n; phi[i++] = i - 1); ^ user.cpp:9:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i <= n; i++) ^ user.cpp:10:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 2 * i; j <= n; phi[j+=i] -= phi[i]) ^ user.cpp:11:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= n;x+=phi[i++]); ^