#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <bitset>
#include <string>
#include <numeric>
#include <functional>
#include <iterator>
#include <typeinfo>
#include <utility>
#include <memory>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <cstddef>
#include <complex>
#include <ctime>
#include <cassert>
using namespace std;

/*¼ÆËãn³öÏÖkµÄ¸öÊý(1<=k<=9)*/
int cal1to9(int n,int k)
{
    int fact = 1,res = 0;
    while(n/fact!=0)
    {
        int high = (n / fact) / 10;
        int low = n % fact;
        int cur = (n-low)%(fact*10)/fact;
        if(cur > k)
            res += (high+1)*fact;
        else if(cur == k)
            res += high*fact + low + 1;
        else
            res += high*fact;
        fact *= 10;
    }
    return res;
}

static inline bool get(int &v)//fast to read huge input
{
    int s = 1, c;
    while(!isdigit(c = getchar())&&c != '-')
    {
        if(c == EOF)
            break ;
    }
    if(c == EOF) return 0;
    if(c == '-') s = 0 , v = 0;
    else v = c^48;
    for(;isdigit(c = getchar());v = (v << 1) + (v << 3) + (c ^ 48));
    v = (s ? v : -v);
    return 1 ;
}

int main()
{
    int n;
    get(n);
    printf("%d\n",cal1to9(n,1)-cal1to9(0,1));
    return 0;
}