Language: C++

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

int main() {
  string S;
  cin>>S;
  vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
  for(int i=0;i<26; i++){
    if(S==X.at(i)){
      cout<<X.at(i+1)<< endl;
    }
  }
}
  

Compiler output:
a.cc: In function 'int main()':
a.cc:7:20: error: 'a' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                    ^
a.cc:7:22: error: 'b' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                      ^
a.cc:7:24: error: 'c' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                        ^
a.cc:7:26: error: 'd' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                          ^
a.cc:7:28: error: 'e' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                            ^
a.cc:7:30: error: 'f' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                              ^
a.cc:7:32: error: 'g' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                ^
a.cc:7:34: error: 'h' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                  ^
a.cc:7:36: error: 'i' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                    ^
a.cc:7:38: error: 'j' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                      ^
a.cc:7:40: error: 'k' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                        ^
a.cc:7:42: error: 'l' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                          ^
a.cc:7:44: error: 'n' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                            ^
a.cc:7:46: error: 'm' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                              ^
a.cc:7:48: error: 'o' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                ^
a.cc:7:50: error: 'p' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                  ^
a.cc:7:52: error: 'q' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                    ^
a.cc:7:54: error: 'r' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                      ^
a.cc:7:56: error: 's' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                        ^
a.cc:7:58: error: 't' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                          ^
a.cc:7:60: error: 'u' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                            ^
a.cc:7:62: error: 'v' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                              ^
a.cc:7:64: error: 'w' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                                ^
a.cc:7:66: error: 'x' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                                  ^
a.cc:7:68: error: 'y' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                                    ^
a.cc:7:70: error: 'z' was not declared in this scope
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                                      ^
a.cc:7:71: error: could not convert '{<expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>, <expression error>}' from '<brace-enclosed initializer list>' to 'std::vector<std::__cxx11::basic_string<char> >'
    7 |   vector<string>X={a,b,c,d,e,f,g,h,i,j,k,l,n,m,o,p,q,r,s,t,u,v,w,x,y,z};
      |                                                                       ^
      |                                                                       |
      |                                                                       <brace-enclosed initializer list>