GCD

#include<stdio.h>int fun(int a,int b){if(b==0) return a;else return fun(b,a%b);}int main(){int a,b,t;while(1){scanf("%d%d",&a,&b);while(b!=0){t=b;b=a%b;a=t;}printf("%d\n",a);scanf("%d%d",&a,&b);printf("%d\n",fun(a,b))； }return 0;}

a%b=r1;

b%r1=r2;

r1%r2=r3;

若余数为0，答案为为被除数。