#include<iostream>
using namespace std;
int n;
int f(int k,int x,int y,int z){
if(k==n)return z;
if(2*x-1==y)f(k+1,x+1,1,1);
else
if(y<x) return f(k+1,x,y+1,z+1);
else return f(k+1,x,y+1,z-1);
}
int main(){
freopen("p1030.in","r",stdin);
freopen("p1030.out","w",stdout);
cin>>n;
cout<<f(1,1,1,1);
fclose(stdin);
fclose(stdout);
return 0;
}
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