ABC f求调

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int mod=998244353;
string s;
int n;
int sum[1000005][10];
int ans;
int fac[2000005],inv[2000005];
int ksm(int a,int b)
{
	int ans=1;
	while(b)
	{
		if(b&1) ans=ans*a%mod;
		a=a*a%mod;
		b>>=1;
	}
	return ans;
}
int C(int n,int m)
{
	if(n>m) return 0;
	return fac[m]*inv[n]%mod*inv[m-n]%mod;
}
signed main()
{
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin>>s;
	n=s.length();
	s=" "+s;
	fac[0]=1;
	for(int i=1;i<=2*n;i++) fac[i]=fac[i-1]*i%mod;
	inv[2*n]=ksm(fac[2*n],mod-2);
	for(int i=2*n-1;i>=1;i--) inv[i]=inv[i+1]*(i+1)%mod;
	for(int i=1;i<=n;i++)
		for(int j=0;j<=9;j++)
			sum[i][j]=sum[i-1][j]+(s[i]==(j+'0'));
	for(int i=1;i<=n;i++)
	{
		int x=sum[i-1][s[i]-'0'-1];
		int y=sum[n][s[i]-'0']-sum[i][s[i]-'0'];
		ans+=C(y+1,x+y);
		ans%=mod;
	}
	cout<<ans;
	return 0;
}