Let \( f:[-1,1]\rightarrow \mathbb{R} \) be defined as \( f(x)=ax^{2}+bx+c \) for all \( x\in [-1,1] \), where \( a,b,c\in \mathbb{R} \) such that \( f(-1)=2 \), \( f'(-1)=1 \) and for \( x\in [-1,1] \) the maximum value of \( f''(x) \) is \( \frac{1}{2} \). If \( f(x)\le \alpha,\, x\in[-1,1] \), then the least value of \( \alpha \) is equal to ________.
