5.5

#include<stdio.h>  
int main()  
{  
    int year,flag;  
    printf("Enter year:");  
    scanf("%d",&year);  
    if(year%4==0&&year%100!=0||year%400==0)  
        flag=1;  
    else  
        flag=0;  
    if(flag==1)  
        printf("%d is a leap year!\n",year);  
    else  
        printf("%d is not a leap year\n",year);  

    return 0;  
}