algorithm - C program that calculates number of days between two dates -

i have written c program calculates number of days between 2 dates. unfortunately, doesn't compile properly. don't know why. can please me fix code? seems there issue scanf , printf functions. don't chance input own date.

this output get: illegal date -1607965827

please me. in advance!

#include <stdio.h> #include <stdlib.h>  int days_in_month[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};  struct date {   int day;   int month;   int year; };  int leap_year(int year) {     if(year%400==0) return 1;      if(year%4==0 && year%100!=0) return 1;      return 0; }  int correct(struct date d) {     if(d.day < 1 || d.day > days_in_month[d.month]) return 0;      if(d.month < 1 || d.month > 12) return 0;      return 1; }  int number_of_days(struct date d) {     int result = 0;     int i;      for(i=1; < d.year; i++) {         if(leap_year(i))             result += 366;         else             result += 365;     }      for(i=1; < d.month; i++) {         result += days_in_month[i];          if(leap_year(d.year) && == 2) result++;     }      result += d.day;     return result; }  int main() {     struct date first, second;     int days;      scanf("%d %d %d", first.day, first.month, first.year);     scanf("%d %d %d", second.day, second.month, second.year);      if(!correct(first) || !correct(second)) {         printf("illegal date\n");     }      days = number_of_days(first) - number_of_days(second);      printf("%d", days);      return 0; } 

you need use addresses of arguments passed scanf (use &)