C :

#include <stdio.h>
#include <stdlib.h>
int f1(int a)
{
    int i=1,sum=0;
    for(i;i<=a;i++)
    sum+=i;
    return sum;
}

int f2(int b)
{
    int sum=0,i=1;
    for(i;i<=b;i++)
    sum+=i*i;
    return sum;
}

double f3(int c)
{
    double sum=0;
    int i=1;
    for(i;i<=c;i++)
    sum+=(double)1/i;
    return sum;
}

int main(int argc, char *argv[])
{
  int a,b,c;
  double sum=0,sum1=0,sum2=0,sum3=0;
  scanf("%d%d%d",&a,&b,&c);
  sum1=f1(a);
  sum2=f2(b);
  sum3=f3(c);
  sum=sum1+sum2+sum3;
  printf("%.2lf\n",sum);

  return 0;
}

C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	int a,b,c;
	cin>>a>>b>>c;
	double sum=0;
	for (int i=1; i<=a; i++) sum+=i;
	for (int i=1; i<=b; i++) sum+=i*i;
	for (int i=1; i<=c; i++) sum+=1.0/i;
	printf("%.2lf\n",sum);
	return 0;
}