PANGRAM STRING OR NOT

PANGRAM STRING OR NOT from Hackerrank.com
https://www.hackerrank.com/challenges/pangrams/problem
Pangrams are sentences constructed by using every letter of the alphabet at least once.
[restrict …]

#include<stdio.h>
#include <stdlib.h>
char* pangrams(char* s)
{
    int i;
    char ch;
    int found = 0;
    int count = 0;
    static char s1[]="pangram";
    static char s2[]="not pangram";
    for(i=0;s[i];i++)
    {
        if((s[i] >= 65) && (s[i] <= 90))
           s[i] = s[i] +32;
    }
    ch = 'a';
    while(ch <= 'z')
    {
            for(i=0;s[i];i++)
            {
                if(s[i] == ch)
                {
                    found = 1;
                    count++;
                    break;
                }
            }
            if(found == 0)
                return s1;
            ch++;
    }
   if(count == 26)
       return s1;
    else
        return s2;
}
int main()
{
    char s1[]="We promptly judged antique ivory buckles for the next prize";
    printf("%s\n",pangrams(s1));
    return 0;
}

[/restrict]