#2，#3，#5 WA求助！！ 感谢各位大佬！！！

#include <stdio.h>
int main()
{
    int a[200],i,j,t,n,num=0,s=0;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    for (i = 1; i < n; i++)
    {  
        for (j = i + 1; j <= n; j++) 
        {  
            if (a[j] < a[i]) 
            {  
                t = a[i];    
                a[i] = a[j];    
                a[j] = t;  
            }  
        }
    }
    for (i=1;i<=n;i++)
    {
        if (a[i]==a[i+1])
        {
            num++;
            s++;
            continue;
        }
        if (a[i]+1==a[i+1])
        {
            num++;
            continue;
        }
        else if (a[i]+1!=a[i+1]&&a[i]!=a[i+1])
        {
            break;
        }
    }
    
    printf("%d",(num-s+1));
    return 0;
}