不开long long 见祖宗,该题可能接近70的时候会越界

#include<iostream>
#include<cmath>
using namespace std;
using ll = long long;
const int N = 75;
ll f[N];
int main()
{
    int n;cin>>n;
    f[1] = 1;
    f[2] = 2;
    for(int i = 3;i <= n;i++)
    {
        f[i] = f[i-1] + f[i-2];
    }
    cout<<f[n]<<"\n";
    return 0; 
}