Tricky of NSUInteger and NSInteger Compare

if NSInteger is negative and the value is smaller than NSUInteger,

the result will be like this:

NSInteger intCount = -1;    //smaller value
NSUInteger uIntCount = 100; //bigger value
NSLog(@"%d", intCount > uIntCount); //to be true (-1 > 100)

why -1 > 100 ? hahaha