#include<bits/stdc++.h>
using namespace std;
int firstoccurance(int a[],int n,int key){
if(n==0){
return -1;
}
if(a[0]==key){
return 0;
}
int i=firstoccurance(a+1,n-1,key);
if(i!=-1){
return i+1;
}
else{
return -1;
}
}
int main() {
int n;
cin>>n;
int a[n];
for(int i=0;i<n;i++){
cin>>a[i];
}
cout<<firstoccurance(a,n,0);
return 0;
}