import std.cstream;void main(){char[]s;for(int n;din.readf(&n,&s)>2;){char[][]t;foreach(j,x;s){foreach(i,c;s)j||(t~=""),t[i]=c~t[i];t.sort;}dout.writefln=t[n];}}
Note that non-ascii characters in the above source code will be escaped (such as \x9f).