100%AC

#include<cstdio>
int gcd(int a,int b){
    int t;
    while(b>0){
        a%=b;
        t=a;a=b;b=t;
    }
    return a;
}
int main(){
    int a,b,c;
    scanf("%d %d %d",&a,&b,&c);
    printf("%d",gcd(gcd(a,b),c));
}