const   fin = 'operatii.in'; fout = 'operatii.out';

procedure main();
var
        n ,i ,a ,b ,sol : longword;
begin
        assign( input, fin ); reset( input );
        assign( output, fout ); rewrite( output );

        a := 0; b := 0; sol := 0;
        readln( n );
        for i := 1 to n do
        begin
                a := b;
                read( b );
                if (b > a) then sol := sol + (b - a);
        end;
        write( sol , #10 );
end;

begin
        main();
end.