void go(int n,int step,int& sum){	n = n - step;	if(n > 0)	{	    go(n,1,sum);		go(n,2,sum);	}	else if(n==0) 	{		sum ++;	}}int main(void)  {	int sum = 0;	go(10,1,sum);	go(10,2,sum);	printf("sum=%d",sum);		return 0;}