hdu 4586 Play the Dice

#include<cstdio>
#define I(x) scanf("%d",&x)
int main()
{
int n,m,t,sum;
while(I(n)!=EOF){
sum=0;
for(int i=0;i<n;i++){
I(t);
sum+=t;
}
I(m);
for(int i=0;i<m;i++) I(t);
if(sum==0) printf("0.00\n");
else if(n==m) printf("inf\n");
else printf("%.2lf\n",1.0*sum/(n-m));
}
return 0;
}