程序，输入字符是算式运作字符就输入2个数计算，如果不是就输出输入错误

#include<cstdio>

int a,b;

char c; 

int main()
{
    c = getchar();
    
    if(c != '+' and c != '-' and c != '*' and c != '/' and c != '%')

        return !printf("input error!");
        
    scanf("%d%d",&a,&b);
    
    if((c == '/' or c == '%')and b == 0) 
    
        return !printf("input error!");
        
    if(c == '+') printf("%d",a + b );
    
    if(c == '-') printf("%d",a - b );
    
    if(c == '*') printf("%d",a * b );
    
    if(c == '/') printf("%d",a / b );
    
    if(c == '%') printf("%d",a % b );
}