#include<stdio.h>
int i,c[100000002],n;
int main ()
{
    freopen("kfib.in","rt",stdin);
    freopen("kfib.out","wt",stdout);
    scanf("%d",&n);
    c[0]=0;
    c[1]=1;
    i=2
    ;
    while(i<=n)
    {
        c[i]=c[i-2]+c[i-1];
        i=i+1;
    }
    printf("%d",c[n]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}