def main():
    import sys
    input = sys.stdin.read().split()
    N = int(input[0])
    A = list(map(int, input[1:N+1]))
    
    current = 0
    for a in A:
        if a == 0:
            current = 0
        elif a == 1:
            current += 1
        else:
            current += 3 + 1*(current//1) if current else 4
    print(current)

if __name__ == "__main__":
    main()