Language: C++

int main(){
  int N;
  char S[10000];
  char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
  scanf("%d␣%s",&N,S);
  for(i=0,i++,(i<10000)&&(S[i]!=nullptr)){
    for(I=0,I++,I<26)
    {
      if(Alph[I]==S[i])
      {
        if(26<I+N){
        S[i] = Alph[I+N-26]
        }else{S[i] = Alph[I+N]}
      }
    }  
  };
  printf(S);
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:4:19: error: 'A' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                   ^
a.cc:4:21: error: 'B' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                     ^
a.cc:4:23: error: 'C' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                       ^
a.cc:4:25: error: 'D' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                         ^
a.cc:4:27: error: 'E' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                           ^
a.cc:4:29: error: 'F' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                             ^
a.cc:4:31: error: 'G' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                               ^
a.cc:4:33: error: 'H' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                 ^
a.cc:4:35: error: 'I' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                   ^
a.cc:4:37: error: 'J' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                     ^
a.cc:4:39: error: 'K' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                       ^
a.cc:4:41: error: 'L' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                         ^
a.cc:4:43: error: 'M' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                           ^
a.cc:4:47: error: 'O' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                               ^
a.cc:4:49: error: 'P' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                 ^
a.cc:4:51: error: 'Q' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                   ^
a.cc:4:53: error: 'R' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                     ^
a.cc:4:57: error: 'T' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                         ^
a.cc:4:59: error: 'U' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                           ^
a.cc:4:61: error: 'V' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                             ^
a.cc:4:63: error: 'W' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                               ^
a.cc:4:65: error: 'X' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                                 ^
a.cc:4:67: error: 'Y' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                                   ^
a.cc:4:69: error: 'Z' was not declared in this scope
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                                     ^
a.cc: In lambda function:
a.cc:4:71: error: expected '{' before ';' token
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                                                                       ^
a.cc: In function 'int main()':
a.cc:4:18: error: array must be initialized with a brace-enclosed initializer
    4 |   char Alph[26]= [A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z];
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:5:3: error: 'scanf' was not declared in this scope
    5 |   scanf("%d␣%s",&N,S);
      |   ^~~~~
a.cc:6:7: error: 'i' was not declared in this scope
    6 |   for(i=0,i++,(i<10000)&&(S[i]!=nullptr)){
      |       ^
a.cc:17:3: error: 'printf' was not declared in this scope
   17 |   printf(S);
      |   ^~~~~~
a.cc:1:1: note: 'printf' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
  +++ |+#include <cstdio>
    1 | int main(){
a.cc:17:12: error: expected ')' before ';' token
   17 |   printf(S);
      |            ^
      |            )
a.cc:6:6: note: to match this '('
    6 |   for(i=0,i++,(i<10000)&&(S[i]!=nullptr)){
      |      ^