from sys import stdin
def main():
    #入力
    readline=stdin.readline
    n=int(readline())
    y=list(map(int,readline().split()))

    i=0
    ans=0
    while i<n:
        if i==0:
            if y[i]>y[i+1]:
                ans+=y[i]-y[i+1]
                y[i]=y[i+1]
        elif 0<i<n-1:
            if y[i-1]>y[i]:
                new_y=y[i-1]
                ans+=abs(new_y-y[i])
                y[i]=new_y
            elif y[i]>y[i+1]:
                new_y=max(y[i-1],y[i+1])
                ans+=abs(new_y-y[i])
                y[i]=new_y
        elif i==n-1:
            if y[i-1]>y[i]:
                new_y=y[i-1]
                ans+=abs(new_y-y[i])
                y[i]=new_y
        i+=1

    print(ans)

if __name__=="__main__":
    main()