#include<cstdio>#include<cstring>const int maxn=161;double dp[maxn][maxn][maxn];int n;void work(int k){dp[1][2][k+1]+=0.5*dp[1][1][k];dp[2][1][k+1]+=0.5*dp[1][1][k];dp[1][n-1][k+1]+=0.5*dp[1][n][k];dp[2][n][k+1]+=0.5*dp[1][n][k];dp[n-1][1][k+1]+=0.5*dp[n][1][k];dp[n][2][k+1]+=0.5*dp[n][1][k];dp[n-1][n][k+1]+=0.5*dp[n][n][k];dp[n][n-1][k+1]+=0.5*dp[n][n][k];for(int i=2;i<n;i++){dp[1][i-1][k+1]+=dp[1][i][k]/3.0;dp[1][i+1][k+1]+=dp[1][i][k]/3.0;dp[2][i][k+1]+=dp[1][i][k]/3.0;dp[n][i-1][k+1]+=dp[n][i][k]/3.0;dp[n][i+1][k+1]+=dp[n][i][k]/3.0;dp[n-1][i][k+1]+=dp[n][i][k]/3.0;if(!(i==(n+1)/2&&k==1)){dp[i-1][1][k+1]+=dp[i][1][k]/3.0;dp[i+1][1][k+1]+=dp[i][1][k]/3.0;dp[i][2][k+1]+=dp[i][1][k]/3.0;}dp[i-1][n][k+1]+=dp[i][n][k]/3.0;dp[i+1][n][k+1]+=dp[i][n][k]/3.0;dp[i][n-1][k+1]+=dp[i][n][k]/3.0;}}int main(){while(~scanf("%d",&n)){memset(dp,0,sizeof(dp));dp[(n+1)/2][(n+1)/2][0]=1;for(int k=0;k<n;k++){work(k);for(int i=2;i<n;i++)for(int j=2;j<n;j++){if(i==(n+1)/2&&j==k)continue;dp[i][j+1][k+1]+=0.25*dp[i][j][k];dp[i][j-1][k+1]+=0.25*dp[i][j][k];dp[i+1][j][k+1]+=0.25*dp[i][j][k];dp[i-1][j][k+1]+=0.25*dp[i][j][k];}}double ans=0;for(int i=1;i<=n;i++)ans+=dp[(n+1)/2][i][i];printf("%0.4lfn",ans);}return 0;}
