C中的项目Euler问题11没有提供任何输出

#include <stdio.h>

int main() {
    int grid[20][20] = {
        // 网格中的数字
    };

    int maxProduct = 0;

    // 水平方向
    for (int i = 0; i < 20; i++) {
        for (int j = 0; j < 17; j++) {
            int product = grid[i][j] * grid[i][j+1] * grid[i][j+2] * grid[i][j+3];
            if (product > maxProduct) {
                maxProduct = product;
            }
        }
    }

    // 垂直方向
    for (int i = 0; i < 17; i++) {
        for (int j = 0; j < 20; j++) {
            int product = grid[i][j] * grid[i+1][j] * grid[i+2][j] * grid[i+3][j];
            if (product > maxProduct) {
                maxProduct = product;
            }
        }
    }

    // 对角线方向
    for (int i = 0; i < 17; i++) {
        for (int j = 0; j < 17; j++) {
            int product = grid[i][j] * grid[i+1][j+1] * grid[i+2][j+2] * grid[i+3][j+3];
            if (product > maxProduct) {
                maxProduct = product;
            }
        }
    }

    // 反对角线方向
    for (int i = 0; i < 17; i++) {
        for (int j = 3; j < 20; j++) {
            int product = grid[i][j] * grid[i+1][j-1] * grid[i+2][j-2] * grid[i+3][j-3];
            if (product > maxProduct) {
                maxProduct = product;
            }
        }
    }

    printf("最大乘积: %d\n", maxProduct);

    return 0;
}