One tire size on both front tires and a different tire size on both back tires?

I bought the car used last year and the original tires that were supposed to come on it from the factory where 21565r60 when I went to change the tires out, I realize that enterprise had put on 21560r70 on all four tires. Now the back four tires are still in good condition and the front are not. But I want to go back to the original tires that were supposed to come on the vehicle, so I bought two 21565r60 to put on both front tires. Will this be a problem that there is one size on both of the front tires and one size on both of the back tires temporarily until I can get them all back to the factory standard tires.