UVa 1388 - Graveyard

/*
ch1, 例题4
*/
#include <cstdio>
#include <algorithm>
#include <cmath>

using namespace std;

int main()
{
#ifndef ONLINE_JUDGE
freopen("in.txt", "r", stdin);
#endif // ONLINE_JUDGE

int n, m;
while(scanf("%d%d", &n, &m) == 2) {
double v, sum = 0.0;
for(int i=1; i<n; i++) {
v = (double)i * (n+m) / n;
sum += abs(v - floor(v+0.5));
}
printf("%.4lf\n", sum*10000/(n+m));
}

return 0;
}