#include <stdio.h>

typedef struct {
    int num;
    char op;
} Expression;

Expression create_expression(int num, char op) {
    Expression e;
    e.num = num;
    e.op = op;
    return e;
}

int evaluate_expression(Expression e) {
    switch (e.op) {
        case '+': return e.num + evaluate_expression(create_expression(0, '+'));
        case '-': return e.num - evaluate_expression(create_expression(0, '+'));
        case '*': return e.num * evaluate_expression(create_expression(0, '+'));
        case '/': return e.num / evaluate_expression(create_expression(1, '+'));
        default: return e.num;
    }
}

int main() {
    int num = 5;
    char op = '+';
    Expression e = create_expression(num, op);
    int result = evaluate_expression(e);
    printf("表达式 %d %c %d = %d
", num, op, num, result);
    return 0;
}