#include <iostream>
#include <vector>
#include <map>
#include <queue>
#include <string>
#include <set>
#include <algorithm>
#include <list>
using namespace std;
using ll = long long int;

int main(){
    int n;
    cin >> n;
    vector<int> v(n);
    for(auto& i : v){
        cin >> i;
    }
    int reset = 0;
    int i = 0;
    vector<bool> ok(n + 1);
    while(i < n){
        ok[(v[i] + reset) % n] = true;
        if(!ok[i]){
            ++reset;
            i = 0;
        }
        else{
            ++i;
        }
    }
    cout << reset << endl;
    return 0;
}