uva10214

/**********author:chanjun2016email:[e-mail]***********/#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>#include <vector>#include <string>#include <map>#include <set>#include <algorithm>using namespace std;#define INF = 0x3f3f3f3fconst int maxa = 2000;const int maxb = 2e6;int phi[maxa + 10];int vis[maxa + 10];void init(){phi[1] = 1;for (int i = 2; i <= maxa; ++i){if (!phi[i]){for (int j = i;j <= maxa; j += i){if (!phi[j]){phi[j] = j;}phi[j] = phi[j] / i * (i - 1);}}}}int gcd(int a,int b){if (!b){return a;}return gcd(b,a % b);}int main(){init();long long a,b;while (scanf("%lld%lld",&a,&b),a && b){long long ans = 0;for (int i = 1; i <= a; ++i){ans += (b / i) * phi[i];for(int j =  b / i * i + 1; j <= b ; ++j){if (gcd(i,j) == 1){++ans;}}}printf("%.7f\n", 1.0 * (ans * 4 + 4) / (double)((2 * a + 1) * (2 * b + 1) - 1));}return 0;}