#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 105
using namespace std;
int n;
int l[maxn<<1];
int main(){
    scanf("%d",&n);
    for(int i=1;i<=2*n;i++)scanf("%d",&l[i]);
    sort(l+1,l+1+2*n);
    int ans=0;
    for(int i=1;i<=2*n;i+=2){
        ans+=l[i];
    }
    printf("%d\n",ans);
    return 0;
}、