HDU 4565 So Easy!

#include <utility>
#include <algorithm>
#include <string>
#include <cstring>
#include <cstdio>
#include <iostream>
#include <iomanip>
#include <set>
#include <vector>
#include <cmath>
#include <queue>
#include <bitset>
#include <map>
#include <iterator>
using namespace std;
#define clr(a,v) memset(a,v,sizeof(a))
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int INF = 0x7f7f7f7f;
const int maxn = 11111;
const int POW = 14;
const double eps = 1e-8;
const int mod = 777777777;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> pii;
typedef vector<LL> VI;
typedef vector<VI> VVI;
typedef vector<VVI> VVVI;
VVI I, E, A;
VVI multi(const VVI& A, const VVI& B, int m) {
VVI res = VVI(2, VI(2, 0));
int i, j, k;
for (i = 0; i < 2; ++i) {
for (j = 0; j < 2; ++j) {
for (k = 0; k < 2; ++k) {
res[i][j] += A[i][k] * B[k][j];
res[i][j] %= m;
}
}
}
return res;
}
VVI cal(const VVI& A, int k, int m) {
VVI res = E, t = A;
while (k) {
if (k & 1)
res = multi(res, t, m);
t = multi(t, t, m);
k >>= 1;
}
return res;
}
int main() {
A = I = E = VVI(2, VI(2, 0));
E[0][0] = E[1][1] = 1;
int a, b, n, m;
while (~scanf("%d%d%d%d", &a, &b, &n, &m)) {
I[0][0] = I[1][1] = a;
I[0][1] = b;
I[1][0] = 1;
A = cal(I, n - 1, m);
LL ans = a * A[0][0] + A[0][1];
ans = (ans << 1) % m;
printf("%I64d\n", ans);
}
return 0;
}