#include
int main()
{
    int n,i;
    scanf("%d",&n);
    int fib[n+2];
    fib[0]=0;
    fib[1]=1;
    for(i=2;i<=n;i++)
    {
        fib[i]=fib[i-1]+fib[i-2];
    }
    printf("%d",fib[n]);
    return 0;
}