read a very big number from string and return that number mod 1000000007

read_mod.cpp

#define INF 1000000007
int read_mod(string num)
{
    int ret = 0;
    for (auto i = num.begin(); i != num.end(); i++) {
        ret = (ret * 10 + (int)(*i) - '0') % INF;
    }
    return ret;
}