three problems - B.c

#include <stdio.h>

int main()
{
    char str[100], ch;
    int i, k;

    k = 0;
    gets(str);
    scanf("%c", &ch);

    for(i = 0; str[i] != '\0'; i++) {
        if(str[i] == ch) {
            if(!k) {
                 printf("character found at position: %d", i+1);
                 k = 1;
            }
            else
                printf(", %d", i+1);
        }
    }

    if(!k)
        printf("Not found.\n");

    return 0;
}