#include<iostream>#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>using namespace std;double d[1010][1010], c[1010][1010];int main(){int i, j, k, n, m;double sum, ans;memset(d,0,sizeof(d));for (i = 0; i <= 1000; i++)c[i][0] = c[i][i] = 1;for (i = 1; i <= 1000; i++)for (j = 1; j < i; j++)c[i][j] = c[i - 1][j - 1] + c[i - 1][j];for (i = 0; i < 1001; i++){if (i < 9)d[i][i] = 1;for (j = 0; j < i; j++)for (int k = 0; k < 9 && j - k > -1; k++)d[i][j] += d[i - k - 1][j - k];}while (scanf("%d%d", &n, &m) != EOF){sum = 0, ans;if (m < 9)ans = 0;else{for (int i = 0; i < 9; i++)for (int j = 0; j + i < 9; j++)sum += d[n - i - j - 2][m - i - j];ans = 1 - sum / c[n][m];}printf("%.6lf%%n", 100 * ans);}}
