BZOJ 4292 Równanie

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
long long k,a,b,ans=0;
bool check(long long x,long long y)
{
    if ((x<a) || (x>b)) return false;
    long long ret=0;
    while (x)
    {
        ret+=(x%10)*(x%10);
        x/=10;
    }
    if (ret!=y) return false;
    return true;
}
int main()
{
    scanf("%lld%lld%lld",&k,&a,&b);
    for (long long i=0;i<=1458;i++)
    {
        if (i*k>b) break;
        if (check(i*k,i))
            ans++;
    }
    printf("%lld\n",ans);
    return 0;
}