用C语言输入一个数N,求N!的值后面后几个0?

int zeros(int n) { unsigned long product; int i, num; if ( n<5 ) return 0; //小于5的数阶乘没有0结尾，不做了 product = 1; for ( i=2; i<=n; i++ ) product *= i; //求阶乘 num = 0; while ( product ) { if ( produ