38 lines
842 B
C++
38 lines
842 B
C++
#include <bits/stdc++.h>
|
|
using namespace std;
|
|
#define int long long
|
|
#define endl "\n"
|
|
|
|
const int N = 4;
|
|
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);
|
|
}
|
|
int main() {
|
|
int b[N][N] = {1, 1, 1, 0};
|
|
int m[N][N] = {
|
|
{1, 1, 1, 0},
|
|
{1, 0, 0, 0},
|
|
{0, 0, 1, 1},
|
|
{0, 0, 0, 1}};
|
|
|
|
cin >> n >> mod;
|
|
for (int i = n - 1; i; i >>= 1) {
|
|
if (i & 1) mul(b, m, b);
|
|
mul(m, m, m);
|
|
}
|
|
|
|
int t = (n * b[0][2]) - b[0][3];
|
|
t = (t % mod + mod) % mod;
|
|
printf("%lld\n", t);
|
|
return 0;
|
|
}
|