/in/foo.c:1:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main(){puts("NO");}
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:1:8: warning: implicit declaration of function 'puts' [-Wimplicit-function-declaration]
 main(){puts("NO");}
        ^~~~