1)

#include <stdio.h>
#define L 26
#define MAXS 1000
int to_lower(int c) {
    if (c >= "A" && c <= "Z")
        return c + 32;
    return c;
}
int main(void) {
    char symbolsS1[L]; for (int i = 0; i < L; ++i) symbolsS1[i] = 0;
    char stringS[MAXS];
    char stringS1[MAXS];
    char ch;
    int i,j;

    printf("Enter s\n");
    for (i = 0; (ch = getchar()) != '\n'; ++i)
        stringS[i] = ch;
    stringS[i] = '\0';

    printf("Enter s1\n");
    for (j = 0; (ch = getchar()) != '\n'; ++j)
        stringS1[j] = ch;
    stringS1[j] = '\0';

    for (int k = 0; k < j; ++k)
        ++symbolsS1[to_lower(stringS1[k]) - 'a'];

    int len = 0;
    for (int k = 0; k < i; ++k)
        if (!symbolsS1[stringS[k] - 'a']) ++len;
    printf("len %d", len);
}