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

char *eur(double a);

int main() {
    double a;
    char *b;
    a = 1234567.891011;
    b = eur(a);
    printf ("%s\n", b);
    return 0;
}

char *eur (double a) {
    int i;
    int l;
    int x;
    char *b;
    char *c;
    b = malloc(30);
    c = malloc(40);
    sprintf(b, "%.2f", a);
    l = strlen(b);
    x = 0;
    c += 40;
    *c = '\0';
    for (i = l - 1; i >= 0; i--)
    {
        b += i;
        if (*b == '.') {
            *b = ',';
        }
        if (i < l - 3) {
            if (x % 3 == 0 && i < l - 4) {
                c--;
                *c = '.';
            }
            x++;
        }
        c--;
        *c = *b;
        b -= i;
    }
    free(b);
    return c;
}