foo.c:1:8: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
 include<algorithm>
        ^
foo.c: In function 'bl':
foo.c:14:1: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
 printf("%c",a[l]);
 ^~~~~~
foo.c:14:1: warning: incompatible implicit declaration of built-in function 'printf'
foo.c:14:1: note: include '<stdio.h>' or provide a declaration of 'printf'
foo.c: In function 'main':
foo.c:20:1: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
 scanf("%s",a);
 ^~~~~
foo.c:20:1: warning: incompatible implicit declaration of built-in function 'scanf'
foo.c:20:1: note: include '<stdio.h>' or provide a declaration of 'scanf'
foo.c:22:3: warning: implicit declaration of function 'strlen' [-Wimplicit-function-declaration]
 n=strlen(a);
   ^~~~~~
foo.c:22:3: warning: incompatible implicit declaration of built-in function 'strlen'
foo.c:22:3: note: include '<string.h>' or provide a declaration of 'strlen'