#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
int a[]={2, 3, -7, 6, 8, 1, -10, 15};
int n=sizeof(a)/sizeof(a[0]);
int i,j=1,count=0;
sort(a,a+n);
for(j=0;j<n;++j)
{
if(a[j]<0)
count++;
}
j=1;
i=count;
while(i<n)
{
if(a[i]!=j)
{
cout<<j;
break;
}
++j;
++i;
}
return 0;
}
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