#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	while(*rp++>=48);
	int a=0,b=0;
	do{
		RD(x);
		a+=x>>1;
		b=b>x?b:x;
	}while(*rp);
	printf("%d",a+(b+1>>1));
}