矩阵快速幂一直输出0求调

#include<iostream>
#include<cstdio>
#include<iomanip>
#include<cmath>
#include<bitset>
#include<algorithm>
#include<set>
#include<map>
#include<vector>
#include<queue>
#include<stack>
#include<cstring>
#include<string>
#define ll long long
#define ull unsigned long long
#define uint unsigned int
#define pii pair<int,int>
#define mp(a,b) make_pair(a,b)
#define endl '\n'

using namespace std;
ll A,B,L,mod;
struct node
{
	ll n,m,a[4][4];
	node operator *(const node &b)const
	{	
		node ans;
		ans.n=n,ans.m=b.m;
		for(int i=1;i<=ans.n;++i)
		{
			for(int j=1;j<=ans.m;++j)
			{
				ans.a[i][j]=0;
				for(int k=1;k<=b.m;++k)
				{
					ans.a[i][j]=(ans.a[i][j]+(a[i][k]%mod)*(b.a[k][j]%mod))%mod;	
				}
			 } 
		}
		return ans; 
	}
}sum;
node fastpow(node a,ll b)
{
	node res=a;--b;
	while(b)
	{
		if(b&1) res=res*a;
		a=a*a; 
		b>>=1;
	}
	return res;
}
inline ll read()
{
	ll x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9')
	{
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9')
	{
		x=(x<<1)+(x<<3)+(ch^48);
		ch=getchar();
	}
	return x*f;
}
inline void write(int x)
{
    if(x<0)
	{
		putchar('-');
		x=-x;
	}
	if(x>9) write(x/10);
    putchar(x%10+'0');
    return;
}

int main()
{
	L=read(),A=read(),B=read(),mod=read();
	sum.n=3,sum.m=1,sum.a[1][1]=0,sum.a[2][1]=A%mod,sum.a[3][1]=1;
	ll maxn=1;
	for(int i=1;i<=18;++i)
	{
		maxn*=10;
		if(A<maxn)
		{
			ll tmp=(maxn-A-1)/B+1;
			if(tmp>L) tmp=L;
        	L-=tmp; 
        	if(tmp)
        	{
        		A+=tmp*B;
				node num;num.n=num.m=3;
				num.a[1][1]=maxn%mod,num.a[1][2]=1,num.a[1][3]=0;
				num.a[2][1]=0,num.a[2][2]=1,num.a[2][3]=B%mod;
				num.a[3][1]=0,num.a[3][2]=0,num.a[3][3]=1;
				sum=fastpow(num,tmp)*sum;
			}
		}
	}
	cout<<sum.a[1][1]<<endl;
    return 0;
}