#include<stdio.h>
#include<algorithm>
#include<limits.h>
using namespace std;
FILE *f=fopen("secv.in","r"),*g=fopen("secv.out","w");
long int n,v[5005],a[5005];

void sorteaza(){
long int i,p=0;
	sort(a+1,a+n+1);
	a[0]=-1;
	for(i=1; i<=n; i++){
		if(a[i]!=a[i-1]){
			p++;
			a[p]=a[i];
		}
	}
	a[0]=p;
}

void parcurgere(){
long int i,j,minimul=LONG_MAX;
	for(i=1; i<=n-a[0]+1; i++){
		if(v[i]==a[1]){
			int post=2;
			for(j=i+1; j<=n && post<=a[0]; j++){
				if(v[j]==a[post]){
					 post++;
				}
			}
			if(post>a[0]){
				minimul=min(minimul,j-i);
			}
		}
	}
	if(minimul==LONG_MAX){fprintf(g,"-1");}
	else{
		fprintf(g,"%ld",minimul);
	}
}

int main(){
	fscanf(f,"%ld\n",&n);
	for(int i=1; i<=n; i++){
		fscanf(f,"%ld ",&v[i]);
		a[i]=v[i];
	}
	sorteaza();
	parcurgere();

return 0;
}