#include <bits/stdc++.h>
using namespace std;
#define sz(x) (ll)(x).size()
#define all(x) (x).begin(), (x).end()
using ll = unsigned long long;
using base = complex<long double>;
const long double PI = acos(-1);
void fft(vector<base>& a, bool inv) {
ll n = sz(a);
for (ll i = 1, j = 0; i < n; i++) {
ll bit = n >> 1;
while (j >= bit) j -= bit, bit >>= 1;
j += bit;
if (i < j) swap(a[i], a[j]);
}
for (ll len = 2; len <= n; len <<= 1) {
vector<base> w(len / 2);
for (ll i = 0; i < len / 2; i++) {
long double ang = 2 * PI * i / len * (inv ? -1 : 1);
w[i] = base(cos(ang), sin(ang));
}
for (ll i = 0; i < n; i += len) {
for (ll j = 0; j < len / 2; j++) {
base u = a[i + j], v = a[i + j + len / 2] * w[j];
a[i + j] = u + v;
a[i + j + len / 2] = u - v;
}
}
}
if (inv) for (ll i = 0; i < n; i++) a[i] /= n;
}
vector<ll> multiply(vector<ll>& a, vector<ll>& b) {
vector<base> fa(all(a)), fb(all(b));
ll n = sz(fa);
fft(fa, false); fft(fb, false);
for (ll i = 0; i < n; i++) fa[i] *= fb[i];
fft(fa, true);
vector<ll> ret(n);
for (ll i = 0; i < n; i++) ret[i] = (ll)(fa[i].real() + (fa[i].real() > 0 ? 0.5 : -0.5));
return ret;
}
ll main() {
cin.tie(0);
ios_base::sync_with_stdio(0);
ll n, m;
cin >> n >> m;
n++, m++;
ll k = 1;
while (k < 2 * max(n, m) - 1) k <<= 1;
vector<ll> a(k), b(k);
for (ll i = 0; i < n; i++) cin >> a[i];
for (ll i = 0; i < m; i++) cin >> b[i];
vector<ll> res = multiply(a, b);
ll ans = 0;
for (ll i = 0; i < n + m - 1; i++) ans ^= res[i];
cout << ans << '\n';
return 0;
}
Compilation message
tt.cpp:48:1: error: '::main' must return 'int'
48 | ll main() {
| ^~
