输入年月日输出是在那一年的第几天

#include<stdio.h>
int main()
{
    int v,sum;
    int leap(int year);//判断闰年
    int add(int month1[],int month,int day);//算天数
    int year,month,day;
    int month1[13]= {0,31,28,31,30,31,30,31,31,30,31,30,31};
    scanf("%d%d%d",&year,&month,&day);
    if(year<=0&&month>0&&month<13&&day>0&&day<32)
    {
        v=leap(year);
        sum=add(month1,month,day);
        if(v==0)
            printf("是第%d天\n",sum);
        else
            printf("是第%d天\n",sum+1);
    }
    else
        printf("输入错误\n");
    return 0;
}
int leap(int year)
{
    int t=0;
    if(year%4==0&&year%100!=0||year%400==0)
        t=1;
    return t;
}
int add(int month1[],int month,int day)
{
    int i,n=0;
    for(i=1; i<month; i++)
    {
        n=n+month1[i];
    }
    n=n+day;
    return n;
}