$$
$$`

```
```language

```
#include<iostream>
using namespace std;

int Number(int n)
{
    int count=0;
    while(n>0)
	{
        int m=n%10;
        if (m==7)
		{
            count++;
        }
        n/=10;
    }
    return count;
}

int main()
{
    int x,y;
    cin>>x>>y;
    int t=0;
    for (int i=x;i<=y;++i) {
        t+=Number(i);
    }
    cout<<t<<endl;
    return 0;
}