Problem when I run my programm

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C

Hello everyone!I have to run a program who read a string from the user and print the string reverse, the character with the most frequences and the character with less frequences.So, i have made two functions but i have a problem when i run my code.My program print the string reverse and after this crashes.Can you help me to find my mistake?For example, when my input is hello world my output is dlrow olleh and after that my program crashes and does not appear the result of my other function.

What I have tried:

Here is my code,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void chars(char *s, char *most_seen, char *less_seen)
{
    char *s2=malloc((strlen(s)+1)*sizeof(char)); //create a new string 
    int i,j,count=0,count1=1,count2=0,count3=100;
    //gets(s1);
    strcpy(s2,s); //copy the s to s2 to compare the strings

    //compare the strings to find the character which appear more in the string 
    for(i=0;i<strlen(s);i++)
    {
        for(j=0;j<strlen(s);j++)
        {
            if(s[i]==s2[j])
                count2++;
        }
        if(count2>count1)
        {
            count1=count2;
            *most_seen=s[i];
        }
        count2=0;
    }
     //compare the strings to find the character which appear less in the string 
     for(i=0;i<strlen(s);i++)
    {
        for(j=0;j<strlen(s);j++)
        {
            if(s[i]==s2[j])
            {
                count++;
            }
        }
        if(count<count3)
        {
            count3=count;
            *less_seen=s[i];
        }
        count=0;
    }
}

char *reverse(char *s)
{
   int l, i;
    char *begin_ptr, *end_ptr, ch;

    // Get the length of the string
    l = strlen(s);

    begin_ptr = s;
    end_ptr = s;

    for (i = 0; i < l - 1; i++)
        end_ptr++;
    for (i = 0; i < l / 2; i++) {
        ch = *end_ptr;
        *end_ptr = *begin_ptr;
        *begin_ptr = ch;

         begin_ptr++;
         end_ptr--;
    }
}

int main()
{
    char *s=malloc(1000*sizeof(char));
    char *s2;
    char mostSeen,lessSeen;

    fgets(s,1000,stdin);
    s[strcspn(s,"\n")] = '\0';

    chars(s,&mostSeen, &lessSeen);
    s2 = reverse(s);

    printf("%s\n",s);
    printf("%s\n",s2);
    printf("%c\n%c\n",mostSeen,lessSeen);

    return 0;
}