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2 years ago
#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
#define int long long
#define endl "\n"
/*
http://ybt.ssoier.cn:8088/problem_show.php?pid=1642
5 1000
5
*/
const int N = 2;
int n, mod;
// 矩阵乘法
void mul(int a[][N], int b[][N], int c[][N]) {
int t[N][N] = {0};
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++)
for (int k = 0; k < N; k++)
t[i][j] = (t[i][j] + (a[i][k] * b[k][j]) % mod) % mod;
}
memcpy(c, t, sizeof t);
}
signed main() {
cin >> n >> mod;
int b[N][N] = {1, 1}; // 结果矩阵(初始化fib[2]=1,fib[1]=1)
// 构造的向量数组
int m[N][N] = {
{1, 1},
{1, 0}};
// 矩阵快速幂
for (int i = n - 1; i; i >>= 1) {
if (i & 1) mul(b, m, b);
mul(m, m, m);
}
printf("%lld\n", b[0][1]);
return 0;
}