C :

#include <stdio.h>
int main()
{
	int m,i,n;
	double f[11000];
	while (scanf("%lf %lf %d",&f[1],&f[2],&m)!=EOF)
	{
		for (i=3;i<=100;i++)
		{
			f[i]=(f[i-1]+1)/f[i-2];
			if (f[i]==f[2])
			{
				if (f[i-1]==f[1])
				{
					n=i-2;
					break;
				}
			}
		}
		m=m%n;
		if (m==0) printf("%.6lf\n",f[n]);
		else printf("%.6lf\n",f[m]);
	}
	return 0;
}

C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
using namespace std;

double ans[6];

int main()
{
	int m;
//	FILE *p,*fp,*f;
//	fp=fopen("E:\\1.out","at");
//	f=fopen("E:\\2.in","r");
//	int cnt=0;
	while(scanf("%lf%lf%d",&ans[1],&ans[2],&m)!=EOF)
	{
	//	cnt++;
		ans[3]=(ans[2]+1)/ans[1];
		ans[4]=(ans[1]+ans[2]+1)/(ans[1]*ans[2]);
		ans[0]=(ans[1]+1)/ans[2];
		char str[10000];
		sprintf(str,"%.6lf",ans[m%5]);
		puts(str);
	//	fprintf(fp,"%s\n",str);
	}
//	printf("%d\n",cnt);
	//fclose(f);
	//fclose(fp);
	return 0;
}

C# :

using System;
class _6052{
 
static void Main()
{
  string s;
  while((s=Console.ReadLine())!=null){
  	double t=0,a,b;int c;
    string []ss=s.Split(' ');
    a=double.Parse(ss[0]);
    b=double.Parse(ss[1]);
    c=(int.Parse(ss[2])-2)%5;/**/
//    Console.WriteLine("{0},{1},{2}",a,b,c);
    if(c==0)Console.WriteLine("{0:f6}",b);
    else {
      while(c--!=0){
  		  t=(b+1)/a;
    	  a=b;
    	  b=t;    
//      Console.WriteLine("{0},{1},{2},{3}",a,b,c,t);
 	  }
//    float tt=12.3456789;
	  Console.WriteLine("{0:f6}",t);
    }
    
  }
       
  
}
        }