program operatii;
var f,g:text;
        n:longint;
procedure iofile;
begin
        assign(f,'operatii.in');reset(f);
        assign(g,'operatii.out');rewrite(g);
        readln(f,n);
end;


procedure solve;
var i:longint;
        sum:int64;
        lx,x:int64;
begin
        lx:=0;
        sum:=0;
        for i:=1 to n do
                begin
                        read(f,x);
                        if x>lx then sum:=sum+x-lx;
                        lx:=x;
                end;
        writeln(g,sum);
        close(f);
        close(g);
end;


begin
        iofile;
        solve;
end.