"readln" after "readf"

[pascal111 via Digitalmars-d-learn]

I've a problem when I'm using "readln" after "readf" that I 
couldn't see my program rest and the lines of the execution ran 
fast:

module main;
import std.stdio;
import std.string;
import std.conv;

int main(string[] args)
{

        char[] yy;
        int x,y,z;


        writef("Enter a number: ");
        readf(" %d",&x);


        writef("Enter a number: ");
        readf(" %d",&y);

        z=x+y;
        writefln("Hi! %d",z);

        writef("Enter a number: ");
        readln(yy);
        yy = strip(yy);
        x=to!int(yy);

        writef("Enter a number: ");
        readln(yy);
        yy = strip(yy);
        y=to!int(yy);

        z=x+y;
        writefln("Hi! %d",z);

        return 0;
    }