#include<cstdio>
using namespace std;
int N,i,j,t,A[250],B[250],C[250];
int main()
{
freopen( "nunta.in" , "r" , stdin );
freopen( "nunta.out" , "w" , stdout );
scanf("%d" , &N );
A[0] = B[0] = A[1] = 1;
B[1] = 2;
for( j = 3 ; j <= N ; ++j )
{
t = 0;
for (i=1; i<=A[0] || i<=B[0] || t; i++, t/=10)
C[i] = (t += A[i] + B[i]) % 10;
C[0] = i - 1;
for( i = 0 ; i <= C[0] ; ++i )
{
A[i] = B[i];
B[i] = C[i];
}
}
if( N == 1 )
printf( "1\n" );
else
{
for( i = B[0] ; i ; --i )
printf("%d" , B[i] );
printf( "\n" );
}
return 0;
}