求调

#include <bits/stdc++.h>

#define int __int128

using namespace std;

using i64 = long long;
using i128 = __int128;
using ull = unsigned long long;
using pii = std::pair < int, int >;

#define fi first
#define se second
#define pc putchar
#define pb push_back
#define ma make_pair
#define eb emplace_back
#define all(x) x.begin(), x.end()

const int N = 1e6 + 10;
int mod = 998244353;
const int inf = 1e18;

void file()
{
	freopen(".in","r",stdin);
	freopen(".out","w",stdout);
}

char buf[1<<15],*p1=buf,*p2=buf;
#define nc() (p1==p2&&(p2=buf+fread(p1=buf,1,1<<15,stdin),p1==p2)?-1:*p1++)
inline int read()
{
    int x=0;char c=nc();
    for(;!isdigit(c);c=nc());
    for(; isdigit(c);c=nc()) x=(x<<3)+(x<<1)+(c^48);
    return x;
}

void print(int x)
{
	if(x<0)	putchar('-'),x=-x;
	if(x>9) print(x/10);
	putchar(x%10+'0');
	return;
}

int n, m;
int a[N], b[N], c[N], d[N];
int sum = 1, cnt1, cnt2;
int ans; 
int fpm(int a, int n)
{
    int res = 1;
    while(n)    
    {
        if(n & 1)   res = res * a % mod;
        a = a * a % mod;
        n >>= 1;
    }
    return res;
}

signed main(void)
{
	// file();
	cin.tie(0),cout.tie(0)->ios::sync_with_stdio(false);
    n = read(), m = read();
    sum = (sum * n * (n + 1) / 2 % mod + mod) % mod;
    sum = (sum * m * (m + 1) / 2 % mod + mod) % mod;
    for(int i = 1;i <= n;i ++)  a[i] = read(), a[i] += a[i - 1];
    for(int i = 1;i <= m;i ++)  b[i] = read(), b[i] += b[i - 1];
    for(int i = 1;i <= n;i ++)  for(int j = i;j <= n;j ++)  c[++ cnt1] = a[j] - a[i - 1];
    for(int i = 1;i <= m;i ++)  for(int j = i;j <= m;j ++)  d[++ cnt2] = b[j] - b[i - 1];
    sort(c + 1, c + cnt1 + 1);
    sort(d + 1, d + cnt2 + 1);
    // for(int i = 1;i <= cnt1;i ++)   print(c[i]), pc(' ');
    // pc('\n');
    // for(int i = 1;i <= cnt2;i ++)   print(d[i]), pc(' ');
    for(int i = 1;i <= cnt2;i++) {
		int pos = upper_bound(c + 1, c + cnt1 + 1, d[i]) - c;
		if(c[pos] > d[i])   ans += (cnt1 - pos + 1);
		ans %= mod;
	}
    print(ans * fpm(sum, mod - 2) % mod), pc('\n');
	return 0;
}