foo.cpp:1:1: error: 'include' does not name a type
 include<algorithm>
 ^~~~~~~
foo.cpp: In function 'int bl(int, int, int, int)':
foo.cpp:14:17: error: 'printf' was not declared in this scope
 printf("%c",a[l]);
                 ^
foo.cpp: In function 'int main()':
foo.cpp:20:13: error: 'scanf' was not declared in this scope
 scanf("%s",a);
             ^
foo.cpp:22:11: error: 'strlen' was not declared in this scope
 n=strlen(a);
           ^