Sereja paint n point plane point number 1 in coordinate i0 then Sereja mark point small large english letter Sereja do not like letter x do not use mark point Sereja think point mark beautifully follow condition hold point divide pair point belong exactly pair pair point less abscissa mark small english letter point large abscissa mark large english letter build square pair pair point square opposite point segment square diagonal result square will not intersect touch one Little Petya erase small large letter mark point now Sereja wonder way return remove letter point mark beautifully