uva10491 - Cows and Cars(牛和车)

大水题，，，，

ans = ncow/(ncow+ncar)  *  ncar/(ncow+ncar-nshow-1)   +   ncar/(ncow+ncar)  *  (ncar-1)/(ncow+ncar-nshow-1);

代码如下：

#include <cstdio>
#include <cmath>

int main ()
{
int car, cow, show;
while(~scanf("%d%d%d",&cow,&car,&show))
{
int n = cow+car;
double ans = 1.0*cow*car/(n*(n-show-1));
ans+=1.0*car*(car-1)/(n*(n-show-1));
printf("%.5lf\n",ans);
}
return 0;
}