Language: C

a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}

Compiler output:
main.c:1:1: warning: data definition has no type or storage class
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      | ^
main.c:1:1: error: type defaults to 'int' in declaration of 'a' [-Wimplicit-int]
main.c:1:3: error: type defaults to 'int' in declaration of 'b' [-Wimplicit-int]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |   ^
main.c:1:5: error: type defaults to 'int' in declaration of 'i' [-Wimplicit-int]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |     ^
main.c:1:7: error: type defaults to 'int' in declaration of 'c' [-Wimplicit-int]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |       ^
main.c:1:9: error: type defaults to 'int' in declaration of 'k' [-Wimplicit-int]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |         ^
main.c:1:17: error: return type defaults to 'int' [-Wimplicit-int]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                 ^~~~
main.c: In function 'main':
main.c:1:28: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                            ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
main.c:1:28: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                            ^~~~~
main.c:1:28: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:50: error: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                  ^~~~
main.c:1:50: note: include '<stdio.h>' or provide a declaration of 'puts'
main.c:1:139: error: implicit declaration of function 'elsefor' [-Wimplicit-function-declaration]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                                                                                                           ^~~~~~~
main.c:1:150: error: expected ')' before ';' token
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                                                                                                                  ~   ^
      |                                                                                                                                                      )
main.c:1:156: error: expected ';' before 'printf'
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                                                                                                                            ^~~~~~
      |                                                                                                                                                            ;
main.c:1:199: error: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                                                                                                                                                                       ^~~~
main.c:1:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
  +++ |+#include <stdlib.h>
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
main.c:1:199: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
    1 | a,b,i,c,k[3100];main(){for(scanf("%d%d",&a,&b);a;puts("")){c=0;for(i=a;i<=b;i++)if(i%400==0||(i%100!=0&&i%4==0))k[c++]=i;if(!c)puts("NA");elsefor(i=0;i<c;)printf("%d\n",k[i++]);scanf("%d%d",&a,&b);}exit(0);}
      |                                                                                                                                                                                                       ^~~~
main.c:1:199: note: include '<stdlib.h>' or provide a declaration of 'exit'