Submission #1606071

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Source Code Expand

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cmath>
#include <iomanip>
#include <cassert>
#include <bitset>
using namespace std;

typedef pair<int, int> P;
#define rep(i, n) for (int i=0; i<(n); i++)
#define all(c) (c).begin(), (c).end()
#define uniq(c) c.erase(unique(all(c)), (c).end())
#define _1 first
#define _2 second
#define pb push_back
#define INF 1145141919
#define MOD 1000000007

int N;
int A[100000];

signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  cin >> N;
  int ctr = 0;
  int cont = 0;
  rep(i, N) {
    cin >> A[i];
    A[i]--;
    if (A[i] == i) {
      cont++;
    }
    else {
      if (cont > 0) ctr += (cont+1)/2;
      cont = 0;
    }
  }
  if (cont > 0) ctr += (cont+1)/2;
  cout <<ctr << "\n";
  return 0;
}

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