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

int main(int argc, char *argv[]){
    char str1[50], str2[50];
    FILE *input1, *input2, *output;
    if (argc != 4){
        printf("Enter 3 file names.\n");
        return 0;
    }
    input1 = fopen(argv[1], "r");
    input2 = fopen(argv[2], "r");
    output = fopen(argv[3], "w");
    if (input1 == NULL || input2 == NULL){
        printf("Error!\n");
        return 0;
    }
    while(!feof(input1) || !feof(input2)){
        if (fgets(str1, 50, input1))
            fprintf(output, "%s", str1);
        if (fgets(str2, 50, input2))
            fprintf(output, "%s", str2);
    }
    printf("Success!\n");
    fclose(input1);
    fclose(input2);
    fclose(output);
    return 0;
}