gcd2 codechef code example

Example: GCD2

#include<stdio.h>
char b[300];
int rem(int a) {
        int p=0,i;
        for(i=0;b[i]!= '\0';i++) p = ((b[i]-'0')+p*10) %a;
        return p;
}

int gcd(int a,int b) {
        if(b==0) return a;
        else gcd(b,a%b);
}

int main() {
        int i,j,a;
        scanf("%d",&i);
        while(i--) {
                scanf("%d %s",&a,b);
                if(a == 0) printf("%s\n",b);
                else {
                        int p = rem(a);
                        printf("%d\n",gcd(a,p));
                }
        }
        return 0;
}