View Compilation Error

0_0_20806118_8496.cpp: In function 'int main()':
0_0_20806118_8496.cpp:10:22: error: conversion from 'arr* {aka a*}' to non-scalar type 'arr {aka a}' requested
     arr a=new arr[num];
                      ^
0_0_20806118_8496.cpp:12:11: error: no match for 'operator[]' (operand types are 'arr {aka a}' and 'int')
     cin>>a[i].s>>a[i].t;
           ^
0_0_20806118_8496.cpp:12:19: error: no match for 'operator[]' (operand types are 'arr {aka a}' and 'int')
     cin>>a[i].s>>a[i].t;
                   ^
0_0_20806118_8496.cpp:16:9: error: no match for 'operator[]' (operand types are 'arr {aka a}' and 'int')
     if(a[i].s<(a[i-1].s+a[i-1].t)/2){
         ^
0_0_20806118_8496.cpp:16:17: error: no match for 'operator[]' (operand types are 'arr {aka a}' and 'int')
     if(a[i].s<(a[i-1].s+a[i-1].t)/2){
                 ^
0_0_20806118_8496.cpp:16:26: error: no match for 'operator[]' (operand types are 'arr {aka a}' and 'int')
     if(a[i].s<(a[i-1].s+a[i-1].t)/2){
                          ^