C :

#include<stdio.h>
int main (){
	float n;
	int s,i,j,k,num;
	while(scanf("%f",&n)!=EOF){
		num = 0;
		n*=10;
		s=1000 - n;
		i=s/100;
		k=s%10;
		j=(s-i*100-k)/10;
		num+=i;
		num+=j;
		num+=k;	
		printf("%d\n",num);
	}
	return 0;
}

C++ :

#include <cstdio>
int a, b, ans;
int main() {
    while(~scanf("%d.%d", &a, &b)) {
        ans = 0;
        a = 1000 - a * 10 - b;
        while(a) {
            ans += a % 10;
            a /= 10;
        }
        printf("%d\n", ans);
    }
}