#include <iostream>
#include <string>
using namespace std;
const int SIZE = 1001;
const int BASE = 10;
string result[SIZE];
string two("2");

void initial()
{
int mcarry, temp, carry;
int k;
string tempResult;
result[1] = "0";
result[2] = "1";
result[3] = "1";
result[4] = "3";
for (int i = 5; i < SIZE; ++i)
{
mcarry = 0;
for (int j = 0; j < two.length(); ++j) /*先做乘法,求出2^(n-3)*/
{
temp = 2 * (two[j] - ‘0‘) + mcarry;
mcarry = temp / BASE; /*乘法进位*/
temp = temp % BASE;
tempResult += (temp + ‘0‘);
}
if (mcarry != 0) /*进位不为0*/
{
tempResult += (mcarry + ‘0‘);
}

two = tempResult; /*存储计算结果*/
tempResult.clear();

int minLength = two.length() > result[i - 2].length() ? result[i - 2].length() : two.length();
carry = 0;

for (k = 0; k < minLength; ++k) /*然后做加法f(n) = f(n -2) + 2^(n - 3)*/
{
temp = (two[k] - ‘0‘) + (result[i - 2][k] - ‘0‘) + carry;
carry = temp / BASE; /*加法进位*/
temp = temp % BASE;
result[i] += (temp + ‘0‘);
}
/*两个数可能长短不一,所以要比较再相加*/
if (minLength < two.length())
{
for(; k < two.length(); k++)
{
temp = (two[k] - ‘0‘) + carry;
carry = temp / BASE;
temp = temp % BASE;
result[i] += (temp + ‘0‘);
}
}
if(minLength < result[i - 2].length())
{
for(; k < result[i - 2].length(); ++k)
{
temp = (result[i - 2][k] - ‘0‘) + carry;
carry = temp / BASE;
temp = temp % BASE;
result[i] += (temp + ‘0‘);
}
}
if (carry != 0) /*进位不为0*/
{
result[i] += (carry + ‘0‘);
}
tempResult.clear();
}
}
int main()
{
int n;
initial(); /*先打表*/
while (scanf ("%d", &n) != EOF)
{
for(int i = result[n].length(); i > 0; --i)
cout << result[n][i - 1]; /*这一步很关键，由于数据是倒着存的,所以要反着输出*/
cout << endl;
}
system ("pause");
return 0;
}

hdu1041