#include<stdio.h>
#include<stdlib.h>
int findFirst(int arr[],int n,int target)
{
    int low=0,high=n-1,result=-1;
    while(low<=high)
    {
        int mid=low+(high-low)/2;
        if(arr[mid]==target){
            result=mid;
            high=mid-1;
        }
        else if(arr[mid]<target)
        {
            low=mid+1;
        }
        else
        {
            high=mid-1;
        }
    }
    return result;
    
}
int findLast(int arr[],int n,int target)
{
    int low=0;
    int high=n-1;
    int result=-1;
    
    while(low<=high)
    {
        int mid=low+(high-low)/2;
        if(arr[mid]==target)
        {
            result=mid;
            low=mid+1;
        }
        else if(arr[mid]<target)
        {
            low=mid+1;
        }
        else
        {
            high=mid-1;
        }
    }
    return result;
}
int main()
{
    int n,x;
    if(scanf("%d",&n)!=1)
    return 1;
    if(n<0)
    {
        printf("Invalid input\n");
        return 0;
    }
    int*arr=(int*)malloc(n*sizeof(int));
    if(arr==NULL)
    return 1;
    for(int i=0;i<n;i++)
    {
        if(scanf("%d",&arr[i])!=1)
        {
            free(arr);
            return 1;
        }
    }
    int first=findFirst(arr,n,x);
    if(first==-1)
    {
        printf("-1\n");
    }
    else
    {
        int last=findLast(arr,n,x);
        printf("%d%d\n",first,last);
    }
    free(arr);
    return ;
}