#include <iostream>
#define M 45
using namespace std;
long long int f[M+1];
long long int fib(int n)
{
if (n > M) {printf("error\n"); return -1;}
if (n == 0) return 1;
if (n == 1)return 1;
if (f[n])
return f[n];
long long int t = fib(n - 1) + fib(n - 2);
f[n] = t;
return t;
}
int main()
{
int n;
while(scanf("%d",&n)==1)
{
printf("%lld\n",fib(n));
}
return 0;
}
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