Program oper;
var fi,fo:text;  i,n,k2,k1,k3:longword;
begin
    assign(fi,'operatii.in'); reset(fi); readln(fi,n);
    assign(fo,'operatii.out'); rewrite(fo);
    for i:=1 to n do begin
                     read(fi,k2);
                     if k2>k1 then k3:=k3+k2-k1;
                     k1:=k2;
                     end;
    write(fo,k3); close(fi); close(fo);
end.