求x的第k位数

#include<stdio.h>int len(int x){if(x<10) return 1;return len(x/10)+1;}int f(int x, int k){if(len(x)-k==0) return x%10;return f(x/10,k);  }int main(){int x = 23574;printf("%d\n", f(x,4));return 0;}