The Fibonacci numbers, commonly denoted F$($n$)$ form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from $0$ and $1.$ That is$,$F$(0)=0,$ F$(1)=1$F$($n$)=$ F$($n $-1)+$ F$($n $-2),$ for n $>1.$Given n$,$ calculate F$($n$).$ Example $1$:Input: n $=2$Output: $1$Explanation: F$(2)=$ F$(1)+$ F$(0)=1+0=1.$Example $2$:Input: n $=3$Output: $2$Explanation: F$(3)=$ F$(2)+$ F$(1)=1+1=2.$Example $3$:Input: n $=4$Output: $3$Explanation: F$(4)=$ F$(3)+$ F$(2)=2+1=3.$ Constraints:$0<=$ n $<=30$