poj 2864 Pascal Library

#include <iostream>#define MAXN 600using namespace std;int _m[MAXN][MAXN];int main(){    int c;    int r;    int i;    int j;    int sum;    while(cin>>c>>r,c||r)    {    for(i = 0; i < r; ++ i)    {        for(j = 0; j < c; ++ j)        { cin>>_m[i][j];        }    }    for(j = 0; j < c; ++ j)    {        sum = 0;        for(i = 0; i < r; ++ i)        { if(_m[i][j] == 0) {     break; }        }        if(i == r)        { cout<<"yes"<<endl; break;        }    }    if(j == c)    {        cout<<"no"<<endl;    }    }}