题解 | The Biggest Water Problem

#include <stdio.h>
int trans(int n)
{
    if(n<10)
        return n;
    int sum=0;
    while(n)
    {
        sum+=n%10;
        n/=10;
    }
    return trans(sum);
}

int main() {
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        printf("%d",trans(n));
    }
    return 0;
}