func_code_string: #include <bits/stdc++.h>   using namespace std;   long long int dp[1000005];   int a[30];   int main() {     int t, k, i, j, n, m, x, y, q, c, d;     dp[0] = 0;     dp[1] = 0;     for (i = 2; i < 1000005; i++)       dp[i] = dp[i / 2] + dp[i - i / 2] + i / 2 * 1LL * (i - i / 2);     cin >> k;     if (k == 0) {       cout <<  a ;       return 0;     }     for (i = 0; i < 26 && k; i++) {       int low = 0, high = 1000000, mid;       while (low < high) {         mid = low + (high - low + 1) / 2;         if (dp[mid] <= k)           low = mid;         else           high = mid - 1;       }       a[i] = low;       k -= dp[low];     }     for (i = 0; i < 26; i++) {       char ch =  a  + i;       if (a[i])         while (a[i]--) cout << ch;     }     return 0;   }   