var f,g:text;
    n,i,j,nrp:longint;
    a:array[1..1000000]of longint;
begin
assign(f,'operatii.in');reset(f);
assign(g,'operatii.out');rewrite(g);
readln(f,n);
for i:=1 to n do
    read(f,a[i]);
i:=1;
while i<=n do
    begin
    if a[i]>0 then begin
                   j:=i;
                   while a[j]>0 do begin
                         a[j]:=a[j]-1;
                         j:=j+1;
                         end;
                   nrp:=nrp+1;
                   i:=1;
                   end;
    i:=i+1;
    end;
writeln(g,nrp);
close(g);
end.