求助大佬，为什么不能边输入边判断

#include<stdio.h>

int main() 
{
    int m,n,count=0,i,j;
    double t;
    scanf("%d %d",&m,&n);
    int a[m][n],b[m][n];
    
    for (i = 0; i < m; i++) {
        for (j = 0; j < n; j++) {
        scanf("%d %d",&a[i][j],&b[i][j]);
        if (a[i][j] == b[i][j])
            count++;
        }
    }
    
    t = count / (m * n)*100;
    printf("%.2f",t);
    
    return 0;
}