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

void variant1(char *res)
{
    for (size_t i = 0; i < 26; i++) {
        res[i] = 'a' + i;
    }
    
    res[26] = '\0';
}

char *variant2(void)
{
    char *res = malloc(27);
    
    if (res) {
        for (size_t i = 0; i < 26; i++) {
            res[i] = 'a' + i;
        }
    
        res[26] = '\0';
    }
    
    return res;
}



int main(void)
{
    char v1[27];
    variant1(v1);
    puts(v1);
    
    char *v2 = variant2();
    if (v2) {
        puts(v2);
        free(v2);
    }
}