How to tone my stomach quickly?

Hey, I am 5ft. 2 or 3 and the last time I checked my weight I was 100, but I think I'm more like 110. I think I'm average weight but I don't know. I wear a size 1 or 1/2. I don't want a 6 pack or even a 4 pack, I think that looks gross on girls but I want a flat stomache, I just want to tone it up. What is the fastest and easiest exersize I can do? Sidups, or leglifts, or what else can I do? Please help!

(size 1 or 1/2 in jeans)

well id say leg lifts. thats what I've been told but im too lazy to do them myself lol...im right there with ya though