#include
int main(){
int a,b,c,n,i;
double s;
scanf("%d",&n);
a=2,b=1,s=0;
for (i=1;i<=n;i ++)
{s+=(a/b);
c=b;
b=a;
a=a+c;
}
printf("s=%f\n",s);
return 0;
}
#include
int main(){
int a,b,c,n,i;
double s;
scanf("%d",&n);
a=2,b=1,s=0;
for (i=1;i<=n;i ++)
{s+=(1.0*a/b); //防止整数运算野昌结果搜洞为整颂漏扒数
c=b;
b=a;
a=a+c;
}
printf("s=%f\n",s);
return 0;
}