FIBO C++

#include<bits/stdc++.h>
using namespace std;

int n;

void giai()
{
    long long f[55];
    f[0]=0;f[1]=1;
    for(int i=2;i<=n;i++) f[i]=f[i-1]+f[i-2];
    cout<<f[n];
}

int main()
{
    freopen("fibo.inp","r",stdin);
    freopen("fibo.out","w",stdout);
    cin>>n;
    giai();

}