func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MaxN = 1;   int n, sol, counter;   bool mark[20];   void check(long long x) {     if (x > n) return;     if (x != 0) sol++;     for (int i = 0; i <= 9; i++) {       if (mark[i]) {         if (i != 0 || (i == 0 && x != 0)) check(x * 10 + i);       } else {         if (counter < 2) {           counter++;           mark[i] = true;           if (i != 0 || (i == 0 && x != 0)) check(x * 10 + i);           mark[i] = false;           counter--;         }       }     }   }   int main() {     scanf( %d , &n);     sol = 0;     counter = 0;     for (int i = 0; i <= 9; i++) mark[i] = false;     long long x = 0;     check(x);     printf( %d n , sol);     return 0;   }   