c program to find the greatest of four numbers

#include<stdio.h>
main() 
{ 
    int a,b,c,d; 
    clrscr(); 
    printf("Enter the Four Numbers :"); 
    scanf("%d %d %d %d",&a,&b,&c,&d); 
    if(a>b) 
    { 
        if(a>c) 
        { 
            if(a>d) 
            {   
                printf("%d is big",a); 
            } 
            else 
            { 
                printf("%d is big",d); 
            } 
        } 
    } 
    else if(b>c) 
        { 
            if(b>d) 
                { 
                    printf("%d is big",b); 
                } 
            else 
                { 
                    printf("%d is big",d); 
                } 
        } 
        else if(c>d) 
            { 
               printf("%d is big",c); 
            } 
        else 
        { 
            printf("%d is big",d); 
        } 
    getch(); 
} 
                                

Enter the Four Numbers : 25 15 20 45
45 is big