Language: C++

#include <bits/stdc++.h>
#include <math.h>
using namespace std;

int main() {
  float N;
  cin >> N;
  float A, B, C, D, E, F, G, H, I, J, K;
  int P, Q, R, S, T, U, V, W, X, Y, Z;
  
  A = fmodf(N, 26*26*26*26*26*26*26*26*26*26);
  P = A-1;
  N = N-A*26*26*26*26*26*26*26*26*26*26
  B = fmodf(N, 26*26*26*26*26*26*26*26*26);
  Q = B-1;
  N = N-B*26*26*26*26*26*26*26*26*26;
  C = fmodf(N, 26*26*26*26*26*26*26*26);
  R = C-1;
  N = N-C*26*26*26*26*26*26*26*26;
  D = fmodf(N, 26*26*26*26*26*26*26);
  S = D-1;
  N = N-D*26*26*26*26*26*26*26;
  E = fmodf(N, 26*26*26*26*26*26);
  T = E-1;
  N = N-E*26*26*26*26*26*26;
  F = fmodf(N, 26*26*26*26*26);
  U = F-1;
  N = N-F*26*26*26*26*26;
  G = fmodf(N, 26*26*26*26);
  V = G-1;
  N = N-G*26*26*26*26;
  H = fmodf(N, 26*26*26);
  W = H-1;
  N = N-H*26*26*26;
  I = fmodf(N, 26*26);
  X = I-1;
  N = N-I*26*26;
  J = fmodf(N, 26);
  Y = J-1;
  N = N-J*26;
  K = N;
  Z = K-1;
  
  vector<int> vec(11);
  vec.at(0) = P;
  vec.at(1) = Q;
  vec.at(2) = R;
  vec.at(3) = S;
  vec.at(4) = T;
  vec.at(5) = U;
  vec.at(6) = V;
  vec.at(7) = W;
  vec.at(8) = X;
  vec.at(9) = Y;
  vec.at(10) = Z;
  
  string Ans; 
  
  for (M = 0; M < 11; M++) {
    if (vec.at(M) == 0)
      Ans += a;
    if (vec.at(M) == 1)
      Ans += b;
    if (vec.at(M) == 2)
      Ans += c;
    if (vec.at(M) == 3)
      Ans += d;
    if (vec.at(M) == 4)
      Ans += e;
    if (vec.at(M) == 5)
      Ans += f;
    if (vec.at(M) == 6)
      Ans += g;
    if (vec.at(M) == 7)
      Ans += h;
    if (vec.at(M) == 8)
      Ans += i;
    if (vec.at(M) == 9)
      Ans += j;
    if (vec.at(M) == 10)
      Ans += k;
    if (vec.at(M) == 11)
      Ans += l;
    if (vec.at(M) == 12)
      Ans += m;
    if (vec.at(M) == 13)
      Ans += n;
    if (vec.at(M) == 14)
      Ans += o;
    if (vec.at(M) == 15)
      Ans += p;
    if (vec.at(M) == 16)
      Ans += q;
    if (vec.at(M) == 17)
      Ans += r;
    if (vec.at(M) == 18)
      Ans += s;
    if (vec.at(M) == 19)
      Ans += t;
    if (vec.at(M) == 20)
      Ans += u;
    if (vec.at(M) == 21)
      Ans += v;
    if (vec.at(M) == 22)
      Ans += w;
    if (vec.at(M) == 23)
      Ans += x;
    if (vec.at(M) == 24)
      Ans += y;
    if (vec.at(M) == 25)
      Ans += z;
  }
  cout << Ans << endl;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:11:33: warning: integer overflow in expression of type 'int' results in '-558124416' [-Woverflow]
   11 |   A = fmodf(N, 26*26*26*26*26*26*26*26*26*26);
      |                ~~~~~~~~~~~~~~~~~^~~
a.cc:13:40: error: expected ';' before 'B'
   13 |   N = N-A*26*26*26*26*26*26*26*26*26*26
      |                                        ^
      |                                        ;
   14 |   B = fmodf(N, 26*26*26*26*26*26*26*26*26);
      |   ~                                     
a.cc:17:33: warning: integer overflow in expression of type 'int' results in '-558124416' [-Woverflow]
   17 |   C = fmodf(N, 26*26*26*26*26*26*26*26);
      |                ~~~~~~~~~~~~~~~~~^~~
a.cc:20:33: warning: integer overflow in expression of type 'int' results in '-558124416' [-Woverflow]
   20 |   D = fmodf(N, 26*26*26*26*26*26*26);
      |                ~~~~~~~~~~~~~~~~~^~~
a.cc:59:8: error: 'M' was not declared in this scope
   59 |   for (M = 0; M < 11; M++) {
      |        ^
a.cc:61:14: error: 'a' was not declared in this scope
   61 |       Ans += a;
      |              ^
a.cc:63:14: error: 'b' was not declared in this scope
   63 |       Ans += b;
      |              ^
a.cc:65:14: error: 'c' was not declared in this scope
   65 |       Ans += c;
      |              ^
a.cc:67:14: error: 'd' was not declared in this scope
   67 |       Ans += d;
      |              ^
a.cc:69:14: error: 'e' was not declared in this scope
   69 |       Ans += e;
      |              ^
a.cc:71:14: error: 'f' was not declared in this scope
   71 |       Ans += f;
      |              ^
a.cc:73:14: error: 'g' was not declared in this scope
   73 |       Ans += g;
      |              ^
a.cc:75:14: error: 'h' was not declared in this scope
   75 |       Ans += h;
      |              ^
a.cc:77:14: error: 'i' was not declared in this scope
   77 |       Ans += i;
      |              ^
a.cc:79:14: error: 'j' was not declared in this scope
   79 |       Ans += j;
      |              ^
a.cc:81:14: error: 'k' was not declared in this scope
   81 |       Ans += k;
      |              ^
a.cc:83:14: error: 'l' was not declared in this scope
   83 |       Ans += l;
      |              ^
a.cc:85:14: error: 'm' was not declared in this scope
   85 |       Ans += m;
      |              ^
a.cc:87:14: error: 'n' was not declared in this scope
   87 |       Ans += n;
      |              ^
a.cc:89:14: error: 'o' was not declared in this scope
   89 |       Ans += o;
      |              ^
a.cc:91:14: error: 'p' was not declared in this scope
   91 |       Ans += p;
      |              ^
a.cc:93:14: error: 'q' was not declared in this scope
   93 |       Ans += q;
      |              ^
a.cc:95:14: error: 'r' was not declared in this scope
   95 |       Ans += r;
      |              ^
a.cc:97:14: error: 's' was not declared in this scope
   97 |       Ans += s;
      |              ^
a.cc:99:14: error: 't' was not declared in this scope
   99 |       Ans += t;
      |              ^
a.cc:101:14: error: 'u' was not declared in this scope
  101 |       Ans += u;
      |              ^
a.cc:103:14: error: 'v' was not declared in this scope
  103 |       Ans += v;
      |              ^
a.cc:105:14: error: 'w' was not declared in this scope
  105 |       Ans += w;
      |              ^
a.cc:107:14: error: 'x' was not declared in this scope
  107 |       Ans += x;
      |              ^
a.cc:109:14: error: 'y' was not declared in this scope
  109 |       Ans += y;
      |              ^
a.cc:111:14: error: 'z' was not declared in this scope
  111 |       Ans += z;
      |              ^