#include <stdio.h>

int main(){
    int n;
    int ans;
    int max;
    int c;
    scanf("%d",&n);
    for (int i=0;i<n;i++) {
        scanf("%d",&c);
        max=(c>max)?c:max;
        ans+=c/2;
    }
    ans+=max/2+max%2;
    printf("%d\n",ans);
}