#include <fstream>

using namespace std;
ifstream fin ("kfib.in");
ofstream fout ("kfib.out");
int k;
long long f1,f2,f3;
int main()
{fin>>k;
f1=0;
f2=1;
k=k-2;
if (k+2==1)
    fout<<0;
else
if (k+2==2)
    fout<<1;
else
if (k+2==3)
    fout<<1;
else
    {while (k>0)
        {f3=f2+f1;
        f1=f2;
        f2=f3;
        k=k-1;
        }
    fout<<f3;
    }
        return 0;
}