runtime error(NJEC)

what does meant by runtime error(NJEC)?
#include<stdio.h>
void main()
{
int i,j,n,temp;
scanf("%d",&n);
int a[n];
for(i=0;i<n;i++)
scanf("%d",&a[i]);
for(i=0;i<(n-1);i++)
{
if(i%2==0)
{
if(a[i]>a[i+1])
{
temp=a[i];
a[i]=a[i+1];
a[i+1]=temp;
}
}
else
{
if(a[i]<a[i+1])
{
temp=a[i];
a[i]=a[i+1];
a[i+1]=temp;
}
}
}
for(i=0;i<n;i++)
printf("%d\t",a[i]);
}

//