judge return character

pascal:

var
number :string;
n,i:integer;
flag:boolean;


begin
readln(number);
n:=length(number);

flag:=true;

for i:=1 to trunc( (n+1)/2 ) do
if number[i]<> number[n+1-i]
then
begin
flag:=false;
break;
end;

writeln(flag);
end.

c:

#include <stdio.h>
#include <stdbool.h>

int str_length(char str[])
{
int len,i;
len=0;
i=0;

while(str[i])
{
    i++;
    len++;
}
    return len;
}


int main(void)
{

char str[1000000];
int n,i;
bool flag;


scanf("%s",str);
n=str_length(str);
flag=true;



for( i=1-1;i<=((n+1)/2 -1);i++  )
{
if(str[i]!= str[n-1-i]  )
{
    flag=false;
    break;
}
}

if(flag)
printf("true");
else
printf("false");
}