why nzec error coming????????????

#include<stdio.h>
#include<stdlib.h>
void main()
{int a=0,m;
scanf("%d",&m);
while(a<m)
{if(a==m)
{printf("YES");
exit(0);}
a=a+1;
if(a==m)
{printf("YES");
exit(1);}
a=a+2;
if(a==m)
{printf("YES");
exit(2);}
a=a+3;}
printf("no");
}