编辑代码

#include <bits/stdc++>
using namespace std;
#define int long long

bool check(int x){
    int cnt=1;
    while(x!=0){
        int t=x%10;
        if(cnt%2==1){
            if(t%2==0) return false;
        }else{
            if(t%2==1) return false;
        }
        x/=10;
        cnt+=1;
    }
}

int main() {
    int n,ans=0;
	cin >> n;
    for(i=0; i<n; i++){
        if (check(i)) ans++;
    }
    cout << ans;
	return 0;
}