#import <Foundation/Foundation.h>
int main() {
	int n;
	scanf("%d",&n);
	long sum=0;
	scanf("%ld",&sum);
	long prev=sum;
	for(int i=0;i<n-2;i++){
		long b;
		scanf("%ld",&b);
		sum+=MIN(b,prev);
		prev=b;
	}
	sum+=prev;
	printf("%ld\n",sum);
}