头文件

#include<bits/stdc++.h>
#define fi first
#define se second
#define io std::ios::sync_with_stdio(false)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const ll mod=1e9+7,INF = 0x3f3f3f3f;
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll exgcd(ll a, ll b, ll &x, ll &y) {if(!b) {x = 1; y = 0; return a;}ll r = exgcd(b, a % b, x, y);ll tmp = x; x = y, y = tmp - a / b * y;return r;}
ll qpow(ll a,ll n){ll r=1%mod;for (a%=mod; n; a=a*a%mod,n>>=1)if(n&1)r=r*a%mod;return r;}
ll qpow(ll a,ll n,ll P){ll r=1%P;for (a%=P; n; a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}
ll EX_BSGS(ll a,ll b,ll p){if(b == 1) return 0;map<ll,ll> pw;ll cnt = 0, t = 1, s, x, m;for(ll d = gcd(a, p); d != 1; d = gcd(a, p)){if(b % d) return -1;++cnt, b /= d, p /= d, t = 1LL * t * a / d % p;
if(b == t) return cnt;}s = b, m = sqrt(p) + 1;for(ll i = 0; i < m; ++i){pw[s] = i;s = 1LL * s * a % p;}x = qpow(a, m, p), s = t;for(ll i = 1; i <= m; ++i){s = 1LL * s * x % p;if(pw.count(s)) return i * m - pw[s] + cnt;
}return -1;} //拔山盖世！
/*ll _next[maxn*2],head[maxn],tot,to[maxn*2];
void add(ll x,ll y)
{
_next[++tot]=head[x],head[x]=tot,to[tot]=y;
//_next[++tot]=head[y],head[y]=tot,to[tot]=x;
}*/