Problem:
Score : 500 points

Problem Statement

Let us denote by f(x, m) the remainder of the Euclidean division of x by m.

Let A be the sequence that is defined by the initial value A_1=X and the recurrence relation A_{n+1} = f(A_n^2, M).
Find \displaystyle{\sum_{i=1}^N A_i}.

Constraints

1 \leq N \leq 10^{10}

0 \leq X < M \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N X M

Output

Print \displaystyle{\sum_{i=1}^N A_i}.

Sample Input 1

6 2 1001

Sample Output 1

1369

The sequence A begins 2,4,16,256,471,620,\ldots Therefore, the answer is 2+4+16+256+471+620=1369.

Sample Input 2

1000 2 16

Sample Output 2

6

The sequence A begins 2,4,0,0,\ldots Therefore, the answer is 6.

Sample Input 3

10000000000 10 99959

Sample Output 3

492443256176507

Solution in Rust (1.42.0) (judge verdict: Accepted)

// template {{{
#![allow(clippy::many_single_char_names)]

#[allow(dead_code)]
mod ngtio {
    use ::std::collections::VecDeque;

    pub struct Buffer {
        buf: VecDeque<String>,
    }

    impl Buffer {
        pub fn new() -> Self {
            Self {
                buf: VecDeque::new(),
            }
        }

        fn load(&mut self) {
            while self.buf.is_empty() {
                let mut s = String::new();
                let length = ::std::io::stdin().read_line(&mut s).unwrap();
                if length == 0 {
                    break;
                }
                self.buf.extend(s.split_whitespace().map(|s| s.to_owned()));
            }
        }

        pub fn string(&mut self) -> String {
            self.load();
            self.buf
                .pop_front()
                .unwrap_or_else(|| panic!("入力が終了したのですが。"))
        }

        pub fn string_char_vec(&mut self) -> Vec<char> {
            let s = self.string();
            s.chars().collect::<Vec<_>>()
        }

        pub fn string_char_vec_trusted_len(&mut self, len: usize) -> Vec<char> {
            let s = self.string();
            let s = s.chars().collect::<Vec<_>>();
            assert_eq!(s.len(), len, "あら、思ったのと長さ違いますね……");
            s
        }

        pub fn char(&mut self) -> char {
            let string = self.string();
            let mut chars = string.chars();
            let res = chars.next().unwrap();
            assert!(
                chars.next().is_none(),
                "char で受け取りたいのも山々なのですが、さては 2 文字以上ありますね？"
            );
            res
        }

        pub fn read<T: ::std::str::FromStr>(&mut self) -> T
        where
            <T as ::std::str::FromStr>::Err: ::std::fmt::Debug,
        {
            self.string()
                .parse::<T>()
                .expect("Failed to parse the input.")
        }

        pub fn read_vec<T: ::std::str::FromStr>(&mut self, len: usize) -> Vec<T>
        where
            <T as ::std::str::FromStr>::Err: ::std::fmt::Debug,
        {
            (0..len).map(|_| self.read::<T>()).collect()
        }
    }

    macro_rules! define_primitive_reader {
        ($($ty:tt,)*) => {
            impl Buffer {
                $(
#[inline]
                    pub fn $ty(&mut self) -> $ty {
                        self.read::<$ty>()
                    }
                )*
            }
        }
    }

    define_primitive_reader! {
        u8, u16, u32, u64, usize,
        i8, i16, i32, i64, isize,
    }

    impl Default for Buffer {
        fn default() -> Self {
            Self::new()
        }
    }
}

#[allow(unused_imports)]
use std::{collections, iter, mem, ops};
// }}}

fn main() {
    let mut buf = ngtio::Buffer::new();
    let n = buf.usize();
    let x = buf.u64();
    let m = buf.u64();
    let mut pow = vec![x];
    let mut ckd = vec![false; m as usize];
    ckd[x as usize] = true;
    let head = loop {
        let y = pow.last().unwrap();
        let y = y * y % m;
        if mem::replace(&mut ckd[y as usize], true) {
            break pow.iter().position(|&z| z == y).unwrap();
        }
        pow.push(y);
    };
    let tail = pow.len() - head;

    let q = n.saturating_sub(head) / tail;
    let r = n - q * tail;
    let ans = pow[..r].iter().sum::<u64>() + q as u64 * pow[head..].iter().sum::<u64>();
    println!("{}", ans);
}