#include<stdio.h>
typedef struct {int y,m,d;}Date;
int mon[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int checkDate(Date date)
{mon[2]=28+(date.y%4==0&&date.y%100||date.y%400==0);
return date.y>0&&date.m>0&&date.d>0&&date.m<13&&date.d<=mon[date.m];
}
int main()
{ Date date;
scanf("%d%*c%d%*c%d",&date.y,&date.m,&date.d);
printf("%s",(checkDate(date)?"OK":"Error"));
return 0;
}