foo.cpp:1:1: error: 'include' does not name a type
 include<iostream> include<math.h> include<stdio.h>
 ^
foo.cpp: In function 'int main()':
foo.cpp:9:1: error: 'cin' was not declared in this scope
 cin>>n>>r;
 ^
foo.cpp:17:33: error: 'pow' was not declared in this scope
 length+=sqrt(pow((x[j+1]-x[j]),2)+pow((y[j+1]-y[j]),2));
                                 ^
foo.cpp:17:55: error: 'sqrt' was not declared in this scope
 length+=sqrt(pow((x[j+1]-x[j]),2)+pow((y[j+1]-y[j]),2));
                                                       ^
foo.cpp:19:33: error: 'pow' was not declared in this scope
 length+=sqrt(pow((x[0]-x[n-1]),2)+pow((y[0]-y[n-1]),2));
                                 ^
foo.cpp:19:55: error: 'sqrt' was not declared in this scope
 length+=sqrt(pow((x[0]-x[n-1]),2)+pow((y[0]-y[n-1]),2));
                                                       ^
foo.cpp:20:9: error: unable to find numeric literal operator 'operator""pir'
 length+=2pir;
         ^
foo.cpp:20:9: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
foo.cpp:21:21: error: 'printf' was not declared in this scope
 printf("%.2f",length);
                     ^
foo.cpp:8:8: warning: unused variable 'pi' [-Wunused-variable]
 double pi=3.1415926535898;
        ^