#include<bits/stdc++.h>
//if atcoder
//#pragma GCC optimize(3)
#define FastIO ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define int long long
#define I using
#define AK namespace
#define CSPS2025 std
I AK CSPS2025;
const int maxn=1e6+10,maxm=1e3+10,mod=998244353;
int t,n,m,x,y,u,v,w,res,ans;
signed main()
{
    cin>>n;
    if(n<=1e16)
    {
        for(int i=0;i<=n;i+=(1000000001))
        {
            string s=to_string(i);
            string p=s;
            reverse(s.begin(),s.end());
            if(s==p)
            {
                u++;
            }
        }   
        cout<<u-1;
        return 0;
    }
    return 0;
}