/in/foo.c: In function 'main':
/in/foo.c:9:2: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  scanf("%d",&n);
  ^~~~~
/in/foo.c:9:2: warning: incompatible implicit declaration of built-in function 'scanf'
/in/foo.c:9:2: note: include '<stdio.h>' or provide a declaration of 'scanf'
/in/foo.c:10:7: error: 'i' undeclared (first use in this function)
  for (i=0;i<26;i++)
       ^
/in/foo.c:10:7: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'perm':
/in/foo.c:57:13: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
             printf("%c", list[i]);      
             ^~~~~~
/in/foo.c:57:13: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:57:13: note: include '<stdio.h>' or provide a declaration of 'printf'
/in/foo.c:58:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("\n");
         ^~~~~~
/in/foo.c:58:9: note: include '<stdio.h>' or provide a declaration of 'printf'