#include <stdio.h>

int main(void) {

int n=30;
int a[n];
int i;
	a[0]=2;
	a[1]=-1;

for(i=2;i<n;i++){
	a[i]=-a[i-1]+a[i-2]+2;
}

printf("a[29]=%d\n",a[29]);

	// your code goes here
	return 0;
}