简单的暴力枚举

#include <bits/stdc++.h>

using namespace std;

bool check(int num)
{
    int sum = 0;
    while(num!=0)
    {
        sum += num%10;
        num /= 10;
    }
    if(sum % 5 == 0) return true;
    return false;
}
int main()
{
    int x,y,ans = 0;
    cin >> x >> y;
    for(int i = x; i <= y; i++)
    {
        if(check(i)) ans++;
    }
    cout << ans << endl;
    return 0;
}