#include<cstdio>
int a[5001],i,j,k,m,n,b[5001],s,e,p=5001,l; 
int main()
{
    freopen("secv.in","r",stdin),
    freopen("secv.out","w",stdout),
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
          scanf("%d",&a[i]);
          if(a[b[m]]<a[i])
                 b[++m]=i;
          for(j=0,k=m;j<k;)
          if(a[b[(j+k)/2]]<a[i])
                 j=(j+k)/2+1;
          else
                 k=(j+k)/2;
          if(a[i]<a[b[j]])
                 b[j]=i;
    }
    for(s=1;s<=b[1];s++)
    {                                 
          for(e=0,i=s;i<b[m];i++)
          for(l=j=1;j<=m&&l;j++)
          if(a[i]==a[b[j]])
                 l=0,e++;
          if(e==b[m]-s&&b[m]-s+1<p)
                 p=b[m]-s+1;
    }
    if(p==5001)
          for(k=2,s=b[1]+1;s<b[m]&&p==5001;s++)
          {
                 for(;b[k]<s;k++);
                 for(e=0,i=s;i<b[m];i++)
                 for(l=1,j=k;j<=m&&l;j++)
                 if(a[i]==a[b[j]])
                       l=0,e++;
                 if(e==b[m]-s&&b[m]-s+1<p)
                       p=b[m]-s+1;
          }
    printf("%d",p==5001?-1:p);
}