#include <bits/stdc++.h>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
    
    
	
	int n;
	cin >> n;
	
	int pos[100010];
	int left = 0; //记录不在本位的个数
	int begin; //记录0开始的位置 
	
	for(int i = 0; i < n; i++){
    
    
		cin >> pos[i];
		if(pos[i] != i){
    
    
			left++;
		}else{
    
    
			pos[i] = -1;
		}
		if(pos[i] == 0){
    
    
			begin = i;
		} 
	}
//	cout << left;
//	cout << "begin:" << begin <<endl;
	
	int num = 0;
	int temp; 
	
	int k = 1;
	
	while(left>0){
    
    
//		cout << "left::::" << left << endl;
		if(begin != 0){
    
     //0不在0位 
			for(int i = 0; i < n; i++){
    
    
				if(pos[i] == begin){
    
    
					pos[begin] = -1;
					pos[i] = 0;
					begin = i;
					num++;
					//cout << i << "  " << pos[i] << endl;
					left--;
					break;
				}
			}	
		}else{
    
    
			while(k < n){
    
    
				if(pos[k] != -1){
    
    
					temp = pos[k];
					pos[k] = pos[0];
					pos[0] = temp;
					begin = k;
					//cout << "i::::" << i << endl;
					num++;
					break;
				}
				else{
    
    
					k++;
				}
			}
		}
		
		
		
		int ii;
		for(ii = 1; ii < n; ii++){
    
    
			if(pos[ii] != -1){
    
    
				break;
			}
		}
		
//		cout << "ii:" << ii << endl;
		if(ii == n){
    
    
			cout << num;
			break;
		}
	}
	return 0;
}