Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

char hennkann(int i) {
    char c　= 'A';
    if (i == 1) {
        c = 'a';
    } else if (i == 2) {
        c = 'b';
    } else if (i == 3) {
        c = 'c';
    } else if (i == 4) {
        c = 'd';
    } else if (i == 5) {
        c = 'e';
    } else if (i == 6) {
        c = 'f';
    } else if (i == 7) {
        c = 'g';
    } else if (i == 8) {
        c = 'h';
    } else if (i == 9) {
        c = 'i';
    } else if (i == 10) {
        c = 'j';
    } else if (i == 11) {
        c = 'k';
    } else if (i == 12) {
        c = 'l';
    } else if (i == 13) {
        c = 'm';
    } else if (i == 14) {
        c = 'n';
    } else if (i == 15) {
        c = 'o';
    } else if (i == 16) {
        c = 'p';
    } else if (i == 17) {
        c = 'q';
    } else if (i == 18) {
        c = 'r';
    } else if (i == 19) {
        c = 's';
    } else if (i == 20) {
        c = 't';
    } else if (i == 21) {
        c = 'u';
    } else if (i == 22) {
        c = 'v';
    } else if (i == 23) {
        c = 'w';
    } else if (i == 24) {
        c = 'x';
    } else if (i == 25) {
        c = 'y';
    } else if (i == 26 || i == 0) {
        c = 'z';
    }
    return c;
}

int main() {
    ll n;
    cin >> n;
  
    vector<int> a;
    
    while (n > 26) {
        int b = n % 26;
        a.push_back(b);
        n /= 26;
        if (b == 0 && n % 26 == 1) {
            n--;
        }
    }
    a.push_back(n % 26);
    for (int i = 0; i < a.size(); i++) {
        cout << a.at(i) << endl;
    }
  
    string ans;
    for (int i = a.size() - 1; i >= 0; i--) {
        char ch = hennkann(a.at(i));
        ans += ch;
    }
    cout << ans << endl;
  
    return 0;
}

Compiler output:
a.cc:6:10: error: extended character 　 is not valid in an identifier
    6 |     char c　= 'A';
      |          ^
a.cc: In function 'char hennkann(int)':
a.cc:8:9: error: 'c' was not declared in this scope
    8 |         c = 'a';
      |         ^
a.cc:10:9: error: 'c' was not declared in this scope
   10 |         c = 'b';
      |         ^
a.cc:12:9: error: 'c' was not declared in this scope
   12 |         c = 'c';
      |         ^
a.cc:14:9: error: 'c' was not declared in this scope
   14 |         c = 'd';
      |         ^
a.cc:16:9: error: 'c' was not declared in this scope
   16 |         c = 'e';
      |         ^
a.cc:18:9: error: 'c' was not declared in this scope
   18 |         c = 'f';
      |         ^
a.cc:20:9: error: 'c' was not declared in this scope
   20 |         c = 'g';
      |         ^
a.cc:22:9: error: 'c' was not declared in this scope
   22 |         c = 'h';
      |         ^
a.cc:24:9: error: 'c' was not declared in this scope
   24 |         c = 'i';
      |         ^
a.cc:26:9: error: 'c' was not declared in this scope
   26 |         c = 'j';
      |         ^
a.cc:28:9: error: 'c' was not declared in this scope
   28 |         c = 'k';
      |         ^
a.cc:30:9: error: 'c' was not declared in this scope
   30 |         c = 'l';
      |         ^
a.cc:32:9: error: 'c' was not declared in this scope
   32 |         c = 'm';
      |         ^
a.cc:34:9: error: 'c' was not declared in this scope
   34 |         c = 'n';
      |         ^
a.cc:36:9: error: 'c' was not declared in this scope
   36 |         c = 'o';
      |         ^
a.cc:38:9: error: 'c' was not declared in this scope
   38 |         c = 'p';
      |         ^
a.cc:40:9: error: 'c' was not declared in this scope
   40 |         c = 'q';
      |         ^
a.cc:42:9: error: 'c' was not declared in this scope
   42 |         c = 'r';
      |         ^
a.cc:44:9: error: 'c' was not declared in this scope
   44 |         c = 's';
      |         ^
a.cc:46:9: error: 'c' was not declared in this scope
   46 |         c = 't';
      |         ^
a.cc:48:9: error: 'c' was not declared in this scope
   48 |         c = 'u';
      |         ^
a.cc:50:9: error: 'c' was not declared in this scope
   50 |         c = 'v';
      |         ^
a.cc:52:9: error: 'c' was not declared in this scope
   52 |         c = 'w';
      |         ^
a.cc:54:9: error: 'c' was not declared in this scope
   54 |         c = 'x';
      |         ^
a.cc:56:9: error: 'c' was not declared in this scope
   56 |         c = 'y';
      |         ^
a.cc:58:9: error: 'c' was not declared in this scope
   58 |         c = 'z';
      |         ^
a.cc:60:12: error: 'c' was not declared in this scope
   60 |     return c;
      |            ^