nCp

#include <stdio.h>

int main() {
    int n;
    char s[100];

    scanf(" %d", &n);
    scanf(" %s", s);

    int cnt = 0;
    for(int a = 0; a < n; ++a)
        for(int b = a + 1; b < n; ++b)
            for(int c = b + 1; c < n; ++c)
                for(int d = c + 1; d < n; d++)
                    printf("%c %c %c %c\n", s[a], s[b], s[c], s[d]), cnt++;

    printf("%d\n", cnt);

    return 0;
}