预测数值关系

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#include<stdio.h>
typedef long long LL;
const int N = 1e6 + 10;
LL f[N];
void init(){
	f[1] = 1;f[2] = 2;f[3] = 3;
	for(int i = 4; i < N; i ++ )f[i] = f[i - 1] + f[i - 3];
}
int op;
int main(){
	init();
	while(1){
		scanf("%d",&op);
		if(!op)break;
		printf("%ld\n",f[op]);
	}
}