洛谷3413 萌数

//Serene
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
using namespace std;
const int maxn=2000+10;
const long long mod=1e9+7;
string l,r;
int len1,len2,a[2][maxn];
long long ans,dp[maxn][12][12][2];

long long f(bool p,int pos,int x,int y,int now) {//4:lim 2:fir 1:cute
	if(!pos) return now&1;
	if(!(now&4)&&dp[pos][x+1][y+1][now&1]!=-1) return dp[pos][x+1][y+1][now&1];
	int g=(now&4)? a[p][pos]:9;long long rs=0;
	for(int i=0;i<=g;++i)
	(rs+=f(p,pos-1,(now&2)&&(!i)? -1:i,x,(now|(i==x||i==y))&(((!i)<<1)|(g==i)<<2|1)))%=mod;
	if(!(now&4)) dp[pos][x+1][y+1][now&1]=rs;
	return rs;
}

int main() {
	cin>>l>>r;
	len1=l.length();len2=r.length();
	for(int i=0;i<len1;++i) a[0][len1-i]=l[i]-‘0‘;
	for(int i=0;i<len2;++i) a[1][len2-i]=r[i]-‘0‘;
	memset(dp,-1,sizeof(dp));ans=f(1,len2,-1,-1,6);
	ans=(ans-f(0,len1,-1,-1,6)+mod)%mod;
	a[0][len1+1]=-1;
	for(int i=len1-1;i>=1;--i) if(a[0][i]==a[0][i+1]||a[0][i]==a[0][i+2]) {
		(ans+=1)%=mod; break;
	}
	printf("%lld",ans);
	return 0;
}