在系数均为整数的时候，可以用NTT代替FFT，这样不会出现精度问题。
#include <bits/stdc++.h>
using namespace std;
typedef long long lld;
const int N = 20000005;
const lld g = 3, mod = 998244353;
lld r[N];
lld powe(lld a, lld b) {
lld base = 1;
while(b) {
if(b & 1) base = base * a % mod;
a = a * a % mod;
b >>= 1;
}
return base;
}
void init(int M)
{
int l = log2(M); r[0] = 0;
for(int i = 1; i < M; i++) {
r[i] = (r[i >> 1] >> 1 | (i & 1) << (l - 1));
}
}
void NTT(vector <lld> &a, int M, int type) {
for(int i = 0; i < M; i++) {
if(i<r[i]) swap(a[i], a[r[i]]);
}
lld Wn, w;
for(int mid = 1; mid < M; mid <<= 1) {
Wn = powe(g, (mod - 1) / (mid << 1));
if(type == -1) Wn = powe(Wn, mod - 2);
int size = mid << 1;
for(int i = 0; i < M; i += size) {
int j = i + mid; w = 1;
for(int k = i; k < j; k++) {
lld x = a[k], y = w * a[k + mid] % mod;
a[k] = (x + y) % mod;
a[k + mid] = (x - y + mod) % mod;
w = w * Wn % mod;
}
}
}
}
vector<lld> conv(vector<lld> a, vector<lld> b) {
int siz = a.size() + b.size();
int M = 1;
while(M < siz) M <<= 1;
a.resize(M); b.resize(M);
init(M); NTT(a, M, 1); NTT(b, M, 1);
for(int i = 0; i <= M; i++) {
a[i] = a[i] * b[i] % mod;
}
NTT(a, M, -1);
lld t = powe(M, mod - 2);
for(int i = 0; i <= M; i++) {
a[i] = a[i] * t % mod;
}
a.resize(siz);
return a;
}
int n, m;
int main() {
// freopen("data.in", "r", stdin);
cin >> n >> m;
vector <lld> a(n + 2), b(m + 2);
for(int i = 0; i <= n; i++) {
cin >> a[i];
}
for(int i = 0; i <= m; i++) {
cin >> b[i];
}
vector <lld> c = conv(a, b);
for(int i = 0; i <= n + m; i++) {
cout << c[i] << " ";
}
return 0;
}