Submission #1591641

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Source Code Expand

#include <vector>
#include <algorithm>
#include <iostream>
#include <cassert>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <cstdio>
#include <ctime>
#include <map>
#include <set>
#include <string>
#include <cassert>

#define INFLL 2000000000000000000
#define INF 2000000000
#define MOD 1000000007
#define PI acos(-1.0)

using namespace std;

typedef pair <int, int> pii;
typedef long long ll;
typedef vector <ll> vll;

int arr[100001];
int n;

int main() {
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	cin >> n;
	int ans = 0;
	int len = 0;
	for (int i = 0; i < n; i++) {
		cin >> arr[i];
		if (arr[i] == i + 1) 
			len++;
		else {
			ans += (len + 1) / 2;
			len = 0;
		}			
	}
	ans += (len + 1) / 2;
	cout << ans << endl;
	return 0;
}

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