CodeForces 907F Power Tower

$Source:$ Codeforces Round #454
$Problem:$ 欧拉降幂公式。改进了一下之前的写法。
$Code:$

#include<bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define pb push_back
#define ALL(A) (A).begin(), (A).end()
#define CLR(A, X) memset(A, X, sizeof(A))
typedef long long LL;
typedef pair<int, int> PII;
const double eps = 1e-10;
const double PI = acos(-1.0);
const auto INF = 0x3f3f3f3f;
int dcmp(double x) { if(fabs(x) < eps) return 0; return x<0?-1:1; }

const int MAXN = 1e5+10;
const LL MOD = 1e9+7;

int a[MAXN], phi[MAXN];

int get(int n) {
    int ret = n;
    for(int i = 2; i*i <= n; i++) if(n%i == 0) {
        ret = ret/i*(i-1);
        while(n%i == 0) n /= i;
    }
    if(n != 1) ret = ret/n*(n-1);
    return ret;
}

int gao(LL x, int m) {
    return x>=m?x%m+m:x;
}

int qpow(int a, int b, int m) {
    int ret = 1;
    while(b) {
        if(b & 1) ret = gao(1LL*ret*a, m);
        a = gao(1LL*a*a, m);
        b >>= 1;
    }
    return ret;
}

int dfs(int l, int r, int i) {
    if(l==r || phi[i]==1) return gao(a[l], phi[i]);
    return qpow(a[l], dfs(l+1, r, i+1), phi[i]);
}

int main() {
    int n, m;
    scanf("%d%d", &n, &m);
    phi[0] = m;
    for(int i = 1; i < 30; i++) {
        phi[i] = get(phi[i-1]);
    }
    for(int i = 1; i <= n; i++) {
        scanf("%d", &a[i]);
    }
    int q;
    scanf("%d", &q);
    while(q--) {
        int l, r;
        scanf("%d%d", &l, &r);
        printf("%d\n", dfs(l, r, 0)%m);
    }
    return 0;
}