#include <stdio.h>
int main(){
    int n,m;
    scanf("%d %d",&n,&m);
    if(n<0 || m<0){
        printf("Invalid input");
        return 0;
    }
    while(m!=0){
        int temp = m;
        n = n%m;
        n = temp;
    }
    printf("%d",n);
}