Greatest Integer+Trigonometric Integrals

$\displaystyle\int_{0}^{n} cos(2\pi\lfloor x \rfloor {x})$ =?

Note:

1. $\lfloor x \rfloor$ denotes greatest integer less than or equal to x.
2. {x} denotes fractional part of x.
3. $\lfloor x \rfloor + {x}=x$

Note :This question is a part of set KVPY 2014 SB