#include<stdio.h>
#define nmax 5050
#define infinit 10000

using namespace std;

FILE *fin=fopen("secv.in","r"),
     *fout=fopen("secv.out","w");

long long c[nmax],a[nmax],s[nmax];
int i,j,k,n,min,sol;
long long aux;

void sort()
{
  for(i=1;i<=n;++i)
  {
  j=i;
  while(j/2 && a[j/2]<a[j])
     {
     aux=a[j/2];
     a[j/2]=a[j];
     a[j]=aux;

     j=j/2;
     }
  }
i=n;
while(i>1)
  {
  aux=a[1];
  a[1]=a[i];
  a[i]=aux;
  i=i-1;

  j=1;
  while(1)
    {
    k=2*j;
    if(k>i) break;
    if(k+1<=i && a[k+1]>a[k]) k=k+1;
    if(a[j] >= a[k]) break;
    aux=a[j];
    a[j]=a[k];
    a[k]=aux;
    j=k;
    }
  }
}

void solve()
{
    int i,j,p,len;
    s[1]=a[1];
    p=2;
    for (i=2; i<=n; i++){
    if (s[p-1]<a[i]) { s[p]=a[i]; p++; } }
    len=p-1;
    for(i=1; i<=n-len+1; i++){
        if (c[i]==min){
            p=1; j=i;
            while (p<len){
                j++;
                if (s[p+1]==c[j]) p++;
                if (p==len) break;
            }
            if (j-i+1<sol) sol=j-i+1;
        }
    }
}

int main()
{
    fscanf(fin,"%d\n",&n);

    for (i=1; i<=n; i++){
        fscanf(fin,"%lld",&c[i]); a[i]=c[i];
    }

    sort();
    sol=infinit;
    min=a[1];
    solve();

    if (sol>n) sol=-1;

    fprintf(fout,"%d\n",sol);
    fclose(fin);
    fclose(fout);
return 0;
}