func_code_string: #include <bits/stdc++.h>   using namespace std;   long long DP[20][4];   void init() {     DP[0][3] = DP[0][2] = DP[0][1] = DP[0][0] = 1;     for (int i = 1; i <= 18; i++) {       DP[i][0] = 1;       for (int j = 1; j <= 3; j++) {         DP[i][j] = 9 * DP[i - 1][j - 1] + DP[i - 1][j];       }     }   }   long long sol(int i, int j, string str) {     if (i == 0) {       if (j >= 0)         return 1;       else         return 0;     }     int d = str[i - 1] -  0 ;     if (d == 0)       return sol(i - 1, j, str);     else if (j == 0)       return 1;     return DP[i - 1][j] + (d - 1) * DP[i - 1][j - 1] + sol(i - 1, j - 1, str);   }   string tostr(long long x) {     string rtn;     while (x) {       rtn += (x % 10 +  0 );       x /= 10;     }     return rtn;   }   string A, B;   long long a, b;   int cas;   int main() {     ios::sync_with_stdio(false);     init();     cin >> cas;     while (cas--) {       cin >> a >> b;       a--;       A = tostr(a);       B = tostr(b);       cout << sol(B.length(), 3, B) - sol(A.length(), 3, A) <<   n ;     }     return 0;   }   