View Code of Problem 71

#include<stdio.h>
int main(){
double a,b,c,sum;
int i,j,n;
a=1;
b=2;
scanf("%d",&n);
for(i=1;i<=n;i++){
	sum=sum+b/a*1.0;
	c=a+b;
	a=b;
	b=c;
}	
printf("%.2f\n",sum);	
	
}