#include <cstdio>

using namespace std;

#define Nmax 500

int A[Nmax], B[Nmax], C[Nmax];

int N;

int main(){

    freopen("nunta.in", "r", stdin);
    freopen("nunta.out", "w", stdout);

    scanf("%d", &N);

    A[0]=1;
    A[1]=2;
    B[0]=1;
    B[1]=1;

    if ( N == 1 ){

        printf("1\n");

        return 0;
    }

    for ( int j = 3; j <= N; j++ ){

        int T = 0, i;

        for ( i = 0; i <= A[0]; i++ )
            C[i] = A[i];

        for ( i = 1; i <= A[0] || i <= B[0] || T; i++, T /= 10 )
            A[i] = ( T += A[i] + B[i] ) % 10;

        A[0] = i - 1;

        for ( i = 0; i <= C[0]; i++ )
            B[i] = C[i];
    }

    for ( int i = A[0]; i; i-- )
        printf("%d", A[i]);

    return 0;
}