poj-3286-How many 0's?

#include<string.h>
#include<algorithm>
#include<stdlib.h>
#include<iostream>
#include<stdio.h>
#include<vector>
#define LL long long
using namespace std;
LL ans(LL x)
{
    if(x<0)return 0;
    LL i,ans;
    i=1;
    ans=1;
    LL y;
    int now;
    while(i*10<=x)
    {
        y=x/(i*10)-1;
        if(y<0)y=0;
        ans+=y*i;
        now=(x/i)%10;
        if(now==0)ans+=x%i+1;
        else ans+=i;
        i=i*10;
    }
    return ans;
}
int main()
{
    LL m,n;
    while(~scanf("%lld%lld",&m,&n)&&(m!=-1||n!=-1))
    {
        cout<<ans(n)-ans(m-1)<<endl;
    }
    return 0;
}