P123 第30题 求杨辉三角的第39行第19列的数

#include<stdio.h>unsigned long c(unsigned long x,unsigned long y){ unsigned long z;     if((y==1)||(y==x))  return 1; z=c(x-1,y-1)+c(x-1,y); return z; } int main(){ unsigned long a,b; while(1) {  printf("请输入两个数，分别为杨辉三角的行和列");  scanf("%u%u",&a,&b);  printf("第%u行第%u列的数为%u\n",a,b,c(a,b)); } return 0;}