var v,x:array[1..100] of integer;
    i,j,n,k:integer;
    f,g:text;
    ok:boolean;
begin
assign(f,'operatii.in');
assign(g,'operatii.out');
reset(f);
rewrite(g);
readln(f,n);
for i:=1 to n do read(f,v[i]);
i:=1;
repeat
j:=i;
ok:=true;
if v[i]<>0 then begin
                k:=k+1;
                repeat
                v[i]:=v[i]-1;
                i:=i+1;
                until v[i]=0;
                end
            else begin ok:=false; i:=i+1;  end;
if ok then i:=j;
until i=n+1;
writeln(g,k);
close(f);
close(g);
end.