#include <stdio.h>
#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    int N;
    scanf("%d", &N);
    int A[N], B[N-1];
    int i=0;
    for(i=0;i<N-1;i++) {
        scanf("%d", &B[i]);
    }
    for(i=0;i<N;i++) {
        A[i] = 100001;
    }
    for(i=0;i<N-1;i++) {
        A[i] = MIN(B[i], A[i]);
        A[i+1] = MIN(B[i], A[i+1]);
    }
    int sum = 0;
    for(i=0;i<N;i++) {
        sum += A[i];
    }
    printf("%d", sum);
    return 0;
}