Codeforces 258C Little Elephant and LCM

Little Elephant and LCM

#include<bits/stdc++.h>
#define LL long long
#define fi first
#define se second
#define mk make_pair
#define PLL pair<LL, LL>
#define PLI pair<LL, int>
#define PII pair<int, int>
#define SZ(x) ((int)x.size())
#define ull unsigned long long
using namespace std;

const int N = 1e5 + ;
const int inf = 0x3f3f3f3f;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const int mod = 1e9 + ;
const double eps = 1e-;

int n, tot, tmp = , ans, a[N], b[N];
vector<int> fac[N];

int power(int a, int b) {
    if(!a) return ;
    int ans = ;
    while(b) {
        if(b & ) ans = 1ll * ans * a % mod;
        a = 1ll * a * a % mod; b >>= ;
    }
    return ans;
}

int main() {
    for(int i = ; i < N; i++)
        for(int j = i; j < N; j += i)
            fac[j].push_back(i);
    scanf("%d", &n);
    for(int i = ; i <= n; i++) scanf("%d", &a[i]);
    sort(a + , a +  + n);
    for(int i = ; i <= a[n]; i++, tot = , tmp = ) {
        for(auto& t : fac[i]) b[++tot] = lower_bound(a + , a +  + n, t) - a;
        for(int i = ; i < tot; i++) tmp = 1ll * tmp * power(i, b[i + ] - b[i]) % mod;
        ans = (ans + 1ll * tmp * power(tot, n +  - b[tot]) % mod) % mod;
        ans = (ans - 1ll * tmp * power(tot - , n +  - b[tot]) % mod + mod) % mod;
    }
    printf("%d\n", ans);
    return ;
}

/*
*/