#include <cstdio>
#include <cstring>

int x[1000],y[1000],z[1000];

void add(int A[], int B[])
{
      int i, t = 0;
      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;
}

int main()
{
	int n,i=0,ok=0;
	freopen("nunta.in","r",stdin);
	freopen("nunta.out","w",stdout);
	scanf("%d",&n);
	x[999]=0;
	y[999]=1;
	x[0]=y[0]=999;
	while(i++<n+1) {
		memcpy(z,x,sizeof(x));
		add(x,y);
		memcpy(y,z,sizeof(z));
	}
	for(i=1; i<=x[0]; i++) {
		if(ok) printf("%d",x[i]);
		if(x[i] && !ok) {
			ok=1;
			printf("%d",x[i]);
		}
	}
	return 0;
}