UVa580 Critical Mass

 1 /*by SilverN*/
 2 #include<algorithm>
 3 #include<iostream>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 #define LL long long
 8 using namespace std;
 9 LL dp[600][4];
10 LL ans[600];
11 LL total;
12 int main(){
13     int i,j;
14     dp[1][0]=1;
15     dp[1][1]=1;
16     for(i=1;i<=30;i++){
17         dp[i][1]+=dp[i-1][0];
18         dp[i][2]+=dp[i-1][1];
19         dp[i][0]+=dp[i-1][0]+dp[i-1][1]+dp[i-1][2];
20     }
21     total=1;
22     for(i=1;i<=30;i++){
23         total<<=1;
24         ans[i]=total-dp[i][0]-dp[i][1]-dp[i][2];
25     }
26     int n;
27     while(scanf("%d",&n) && n){
28         printf("%d\n",ans[n]);
29     }
30     return 0;
31 }