5 pizda

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

int check(int a){
    return a < 0 || a > 255;
}
char * int_bin(int a){
    char* ans = (char*)malloc(9 * sizeof(char));
    for (int i = 0; i < 8; ++i){
        ans = '0';
    }
    for (int i = 0; i < 8; ++i){
        int c1 = (a >> (7 - i));
        int c2 = c1 % 2;
        if (c2>0)
            ans[i] = '1';
    }
    ans[8] = '\n';
    return ans;
}
int main() {
    int a1, a2, a3, a4;
    scanf("%d.%d.%d.%d", &a1, &a2, &a3, &a4);
    int b1, b2, b3, b4;
    scanf("%d.%d.%d.%d", &b1, &b2, &b3, &b4);
    if(check(a1) || check(a2) || check(a3) || check(a4)){
        printf("wrong IP");
        return 0;
    }
    else if (check(b1) || check(b2) || check(b3) || check(b4)){
        printf("wrong MASK");
        return 0;
    }
    char * mask = "";
    mask = int_bin(b1);
    strcat(mask, int_bin(b2));
    strcat(mask, int_bin(b3));
    strcat(mask, int_bin(b4));
    int was0 = 0;
    for (int i = 0; i <32; ++i){
        if (mask[i]=='1' && !was0)
            continue;
        else if (mask[i] == '0')
            was0 = 1;
        else{
            printf("wrong MASK");
            return 0;
        }
    }
    printf("%d.%d.%d.%d", a1 & b1, a2 & b2, a3 & b3, a4 & b4);


    return 0;
}