今有一数列0,1,1,2,3,5,8,13,21,…..编程实现求数列的第n项的值

#include<iostream>
using namespace std;
int F(int);
void main()
{
int n;
cin>>n;
cout<<F(n)<<endl;
}
int F(int x)
{
if(x==1)
return 0;
else if(x==2)
return 1;
else
return F(x-1)+F(x-2);
}

F(int n)
{
if(n==0 || n==1)return n;
return F(n-1)+F(n-2);
}

F(n)
int n
{
if(n==0)return 0;
if(n==1)return 1;
return F(n-1)+F(n-2);
}
main()
{
int n,m;
printf("\n Enter a integer:");
scanf("%d",&n);
m=F(n);
printf("\n 第%d项是%d",n,m);
}