Submission #1131270

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define all(c) c.begin(),c.end()
#define pb push_back
#define fs first
#define sc second
#define show(x) cout << #x << " = " << x << endl
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
using namespace std;
template<class S,class T> ostream& operator<<(ostream& o,const pair<S,T> &p){return o<<"("<<p.fs<<","<<p.sc<<")";}
template<class T> ostream& operator<<(ostream& o,const vector<T> &vc){o<<"sz = "<<vc.size()<<endl<<"[";for(const T& v:vc) o<<v<<",";o<<"]";return o;}
int N;
int x[100000];
typedef long long ll;
ll mod=1e9+7;
int main(){
	cin>>N;
	rep(i,N) cin>>x[i];
	ll ans=1;
	int j=0;
	rep(i,N){
		while(j<N&&x[j]>2*(j-i)) j++;
		ans*=(min(N,j+1)-i);
		ans%=mod;
//		show(j+1-i);
	}
	cout<<ans<<endl;
}

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