#include <stdio.h>
int main(){
    int a, b,c;
    scanf_s("%d",&a);
    scanf_s("%d",&b);
    c = a + b;
    return 0;
}

//the result is wrong answer,I want to ask why?Can you help me fix it?

You don't have a sense of output statement.

#include <stdio.h>
int main ()
{
    int a, b, c;
    scanf("%d", &a);
    scanf("%d", &b);
    c = a + b;
    printf("%d", c);
    return 0;
}