View Compilation Error

0_0_28794474_28135.cpp:1:1: error: 'include' does not name a type
 include<bits/stdc++.h>
 ^
0_0_28794474_28135.cpp:9:12: error: 'string' was not declared in this scope
 num change(string a){
            ^
0_0_28794474_28135.cpp:9:21: error: expected ',' or ';' before '{' token
 num change(string a){
                     ^