Armstrong number prototype

#include<stdio.h>
#include<math.h>

void main()
{
    int n,t,sum,r,c;
    puts("Enter a number");
    scanf("%d",&n);

    t=n;
    while(t!=0)
    {
        r=t%10;
        sum = sum + round(r*r*r);
        t=t/10;
    }
    if(sum==n) puts("Armstrong number");
    else puts("Not Armstrong number");
}