#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    ll n; cin >> n;
    n = n / (1e9+1);

    int ans = 0;

    // cout << n << endl;
    srep(ii,1000,10000){
        int i = ii;
        int a = i % 10; i /= 10;
        int b = i % 10; i /= 10;
        int c = i % 10; i /= 10;
        int d = i % 10; i /= 10;
        int x = 10000001*a + 1000010*b + 100100*c + 11000*d;
        while(x % 10 == 0) x /= 10;
        ans += (x<=n);
        // if(x<=n) cout << x << endl;
    }

    srep(ii,10000,100000){
        int i = ii;
        int a = i % 10; i /= 10;
        int b = i % 10; i /= 10;
        int c = i % 10; i /= 10;
        int d = i % 10; i /= 10;
        int e = i % 10; i /= 10;
        int x = 100000001*a + 10000010*b + 1000100*c + 101000*d + 10000*e;
        while(x % 10 == 0) x /= 10;
        ans += (x<=n);
        // if(x<=n) cout << x << endl;
    }



    cout << ans << endl;
    return 0;
}