#include<stdio.h>
int main()
{
int a,b,c;
scanf("%d%d%d",&a,&b,&c);
double sum=0;
int sum1=0,sum2=0;
double sum3=0;
for(int i=1;i<=a;i++)
{
sum1+=i;
}
for(int j=1;j<=b;j++)
{
sum2+=j*j;
}
for(int k=1;k<=c;k++)
{
double s=k;
sum3 +=1/s;
}
sum=sum1+sum2+sum3;
printf("%.2f\n",sum);
return 0;
}