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

void eprint(char *msg){
fprintf(stderr, "%s\n", msg);
exit(1);
}

int main(){
regex_t expr;
if (regcomp(&expr, "(1|0)+", 0) != 0) eprint("regcomp failed!");
int ret = regexec(&expr, "1010", 0, NULL, 0);
printf("%d\n", ret);
}