Language: C++

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

int main() {
    long dog;
    cin>>dog;
    if(dog == 1) cout<<a<<endl;
    if(dog == 2) cout<<b<<endl;
    if(dog == 3) cout<<c<<endl;
    if(dog == 4) cout<<d<<endl;
    if(dog == 5) cout<<e<<endl;
    if(dog == 6) cout<<f<<endl;
    if(dog == 7) cout<<g<<endl;
    if(dog == 8) cout<<h<<endl;
    if(dog == 9) cout<<i<<endl;
    if(dog == 10) cout<<j<<endl;
    if(dog == 11) cout<<k<<endl;
    if(dog == 12) cout<<l<<endl;
    if(dog == 13) cout<<m<<endl;
    if(dog == 14) cout<<n<<endl;
    if(dog == 15) cout<<o<<endl;
    if(dog == 16) cout<<p<<endl;
    if(dog == 17) cout<<q<<endl;
    if(dog == 18) cout<<r<<endl;
    if(dog == 19) cout<<s<<endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:7:24: error: 'a' was not declared in this scope
    7 |     if(dog == 1) cout<<a<<endl;
      |                        ^
a.cc:8:24: error: 'b' was not declared in this scope
    8 |     if(dog == 2) cout<<b<<endl;
      |                        ^
a.cc:9:24: error: 'c' was not declared in this scope
    9 |     if(dog == 3) cout<<c<<endl;
      |                        ^
a.cc:10:24: error: 'd' was not declared in this scope
   10 |     if(dog == 4) cout<<d<<endl;
      |                        ^
a.cc:11:24: error: 'e' was not declared in this scope
   11 |     if(dog == 5) cout<<e<<endl;
      |                        ^
a.cc:12:24: error: 'f' was not declared in this scope
   12 |     if(dog == 6) cout<<f<<endl;
      |                        ^
a.cc:13:24: error: 'g' was not declared in this scope
   13 |     if(dog == 7) cout<<g<<endl;
      |                        ^
a.cc:14:24: error: 'h' was not declared in this scope
   14 |     if(dog == 8) cout<<h<<endl;
      |                        ^
a.cc:15:24: error: 'i' was not declared in this scope
   15 |     if(dog == 9) cout<<i<<endl;
      |                        ^
a.cc:16:25: error: 'j' was not declared in this scope; did you mean 'jn'?
   16 |     if(dog == 10) cout<<j<<endl;
      |                         ^
      |                         jn
a.cc:17:25: error: 'k' was not declared in this scope
   17 |     if(dog == 11) cout<<k<<endl;
      |                         ^
a.cc:18:25: error: 'l' was not declared in this scope
   18 |     if(dog == 12) cout<<l<<endl;
      |                         ^
a.cc:19:25: error: 'm' was not declared in this scope; did you mean 'tm'?
   19 |     if(dog == 13) cout<<m<<endl;
      |                         ^
      |                         tm
a.cc:20:25: error: 'n' was not declared in this scope; did you mean 'yn'?
   20 |     if(dog == 14) cout<<n<<endl;
      |                         ^
      |                         yn
a.cc:21:25: error: 'o' was not declared in this scope
   21 |     if(dog == 15) cout<<o<<endl;
      |                         ^
a.cc:22:25: error: 'p' was not declared in this scope
   22 |     if(dog == 16) cout<<p<<endl;
      |                         ^
a.cc:23:25: error: 'q' was not declared in this scope
   23 |     if(dog == 17) cout<<q<<endl;
      |                         ^
a.cc:24:25: error: 'r' was not declared in this scope
   24 |     if(dog == 18) cout<<r<<endl;
      |                         ^
a.cc:25:25: error: 's' was not declared in this scope
   25 |     if(dog == 19) cout<<s<<endl;
      |                         ^