我觉得是当a/b<1的时候，这个方法会出错，能帮忙看一下怎么精化一下吗

#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<cmath>
#include<algorithm>
using namespace std;
int a,b,n,s;
double x; 
int main(){
	scanf("%d%d%d",&a,&b,&n);
	double sum=a/b;
	if(sum<1)
		sum+=1;
	while(x!=n){
		double s2=sum*10;
		s=(int)s2%10;
		++x;
	}
	printf("%d",s);
	return 0;
}