Python

Pick the Points

There are many sets of points on the horizontal axis of a co$-$ordinate plane. If a point is plotted in between any set, that set is reduced to that point. Given X sets, find the minimum number of points one should pick to reduce all the points to minimum number of points.

Input Specification:

input$1$: X$.$ number of sets.

input$2$: Array consisting of X pairs, each pair indicating start and end of a set.

Output Specification:

Return an integer number as per the question.

Example $1$:

input$1$: $3$

input$2$: $((1\mathrm{.}3)(2\mathrm{.}5).(3\mathrm{.}6))$

Output: $1$

Example $2$:

input $1$:$3$

input$2$: $((1\mathrm{.}3).(2\mathrm{.}5).(6\mathrm{.}9))$

Output: $2$