Language: C

double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}

Compiler output:
main.c:1:15: error: return type defaults to 'int' [-Wimplicit-int]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |               ^~~~
main.c: In function 'main':
main.c:1:28: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                            ^~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
  +++ |+#include <stdio.h>
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
main.c:1:28: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                            ^~~~~
main.c:1:28: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:1:45: error: invalid operands to binary % (have 'double' and 'int')
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                                          ~~~^
      |                                           |
      |                                           double
main.c:1:51: error: invalid operands to binary % (have 'double' and 'int')
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                                                   ^
main.c:1:55: error: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                                                       ^~~~
main.c:1:55: note: include '<stdio.h>' or provide a declaration of 'puts'
main.c:1:60: error: implicit declaration of function 'fabs' [-Wimplicit-function-declaration]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                                                            ^~~~
main.c:1:1: note: include '<math.h>' or provide a declaration of 'fabs'
  +++ |+#include <math.h>
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
main.c:1:60: warning: incompatible implicit declaration of built-in function 'fabs' [-Wbuiltin-declaration-mismatch]
    1 | double p[9],i;main(){for(;~scanf("%lf",p+i++%8);)i%8||puts(fabs((p[2]-*p)*(p[6]-p[4])+(p[3]-p[1])*(p[7]-p[5]))<1e-7?"YES":"NO");}
      |                                                            ^~~~
main.c:1:60: note: include '<math.h>' or provide a declaration of 'fabs'