Thread: how can i write it shorter?

so i'm beginner and i think this is weird(in if and do function) have another easy way?
sorry for my bad english

Code:

#include"stdio.h"
int main(){
    int a,b,c,sum=0;


do{    printf("put  A : ");
scanf("%d",&a);
}
while(a>30);


do{    printf("put  B : ");
scanf("%d",&b);
}
while(b>30);


do{    printf("put  C : ");
scanf("%d",&c);
}
while(c>40);


sum=a+b+c;
//printf("sum = %d",sum);


if(sum>=80){ printf("A");}
if(sum>=75&&sum<=79){ printf("B+");}
if(sum>=70&&sum<=74){ printf("B");}
if(sum>=65&&sum<=69){ printf("C+");}
if(sum>=60&&sum<=64){ printf("C");}
if(sum>=55&&sum<=59){ printf("D+");}
if(sum>=50&&sum<=54){ printf("D");}
if(sum<50){ printf("F");}
}

Some food for thought: You may want to consider a look up table

If you had an array of strings with 20 elements, you could do something like this...

Code:

result=lookupArray[total/5];