#include<bits/stdc++.h>
#pragma GCC optimize(2)
#define For(i,a,b) for(register ll i=a;i<=b;i++)
#define Down(i,a,b) for(register ll i=a;i>=b;i--)
using namespace std;
typedef long long ll;
typedef string str;
typedef double db;
const ll inf=0x3f3f3f3f3f3f3f3f;
inline ll read(){
    ll x=0,f=1;
    char c=getchar();
    while(!isdigit(c)) f=(c=='-')?-1:f,c=getchar();
    while(isdigit(c)) x=x*10+c-'0',c=getchar();
    return x*f;
}
inline ll write(ll x){
	if(x<0){
		putchar('-');
		x=-x;
	}
	if(x>9) write(x/10);
	putchar(x%10+'0');
}
ll n,a[1000100];
int main(){
	cin>>n;
	a[1]=1;
	a[2]=2;
	For(i,3,n) a[i]=(a[i-1]+a[i-2])%15746;
	cout<<a[n];
    return 0;
}

猪CTJer HAPPY

#include<bits/stdc++.h>
#define ll long long
#pragma GCC optimize(2)
#define un unsigned
#define int long long
#define db double
#define st string
#define ct const
#define xh(a,b,c) for(int a=b;a<=c;a++)
#define wx while(1)
#define dn(a,b,c) for(int a=b;a>=c;a--)
using namespace std;
int f[1000010],n;
signed main(){
	cin>>n;
	f[1]=1,f[2]=2;
	xh(i,3,n)f[i]=(f[i-1]+f[i-2])%15746;
	cout<<f[n];
	return 0;
}

#include<bits/stdc++.h> using namespace std; long long n,i,a[1050000]; int main(){ ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); cin>>n; a[1]=1; a[2]=2; for(i=3;i<=n;i++) a[i]=(a[i-1]+a[i-2])%15746; cout<<a[n]; return 0; }

就是斐波那契数列

#include<bits/stdc++.h>
using namespace std;
long n,i,a[1000500];
int main()
{
   cin>>n;
   a[1]=1;
   a[2]=2;
   for(i=3;i<=n;i++)a[i]=(a[i-1]+a[i-2])%15746;
   cout<<a[n];
   return 0;
}