四則演算：二項

#include<stdio.h>
#include<string.h>
#include <stdlib.h>
int main(void){
    int kou1;
    char enzan = 0;
    int kou2;
    char eq;
    int ans = 0;
    scanf( "%d%c%d%c", &kou1, &enzan, &kou2, &eq );
    if (enzan == 0x2b){
      ans = kou1 + kou2;
    } else if (enzan == 0x2d){
      ans = kou1 - kou2;
    } else if (enzan == 0x2a){
      ans = kou1 * kou2;
    } else if (enzan == 0x2f){
      ans = kou1 / kou2;
    } else {
      printf("Error! Please check your fomula.\n");
      exit(0);
    }
    printf("%d\n",ans);
}