I need Visa? (St. Petersburg)

Hello everyone!

I am Uruguayan citizen and as many other latinamerican citizenships we dont need visa to enter Rusia and we are allowed to spend up to 90 days in a period of Protected content .

I already spent 90 days in Russia, then went out and came back on a student visa for 3 months.

My question is, once my visa expires, I can go out from Russia and come back few days later with no visa? I dont really understand if the 90 days spent in Russia on a student visa counts for the rule of the 90 days on a period of 180.

I know I should ask first at the embassy, but they are taking lots of time to answer, that's why I hope someone here can help me.

Thank you in advance,

Francisco.