acwing 恨7不成妻

#include <iostream>
#include<cstring>
#include<algorithm>
using namespace std;
#define ll long long
#define endl "\n"
#define LOCAL
#define pb push_back
#define int    long long
int l,r;
int a[40];
int mod=1e9+7;
struct node
{
    int c;
    int sum;
    int sumr;
};
node f[40][12][12];
int pos[40];
node dfs(int len,int s,int k,int flag)//s每一位数位和取余7，这个整数取余7
{
    if(!len)
    {
        return (node){(s&&k),0,0};
    }
    if(!flag&&f[len][s][k].c!=-1) return f[len][s][k];
    int up=flag?a[len]:9;
    node ans={0,0,0};
    for(int i=0;i<=up;i++)
    {
        if(i==7) continue;
        node te=dfs(len-1,(s+i)%7,(k*10+i)%7,flag&&i==a[len]);
        ans.c=(ans.c+te.c)%mod;
        ans.sum=((ans.sum+te.sum)%mod+pos[len-1]*te.c%mod*i%mod)%mod;
        ans.sumr=(ans.sumr+te.sumr+2*i%mod*pos[len-1]%mod*(te.sum)%mod+i*pos[len-1]%mod*i%mod*pos[len-1]%mod*te.c%mod)%mod;
    }
    if(!flag) f[len][s][k]=ans;
    return ans;
}
int cal(int x)
{
    int len=0;
    memset(f,-1,sizeof(f));
    while(x)
    {
        a[++len]=x%10;
        x/=10;
    }
    return dfs(len,0,0,1).sumr;
}
void solve()
{
    cin>>l>>r; 
      cout<<(cal(r)-cal(l-1)+mod)%mod<<endl;
}
signed main() {
std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    //#ifdef LOCAL
    //freopen("data.in.txt","r",stdin);
    //freopen("data.out.txt","w",stdout);
    //#endif
    int __ = 1;
    pos[0]=1;
    for(int i=1;i<=40;i++)
    {
        pos[i]=pos[i-1]*10%mod;
    } 
    cin>>__;
    while (__--)
        {
            solve();
        }
    return 0;
}