改写程序代码：求s=1+3+5+……+99的值

main(){
int i,sum=0;
for (i=1;i<=99;i+=2) sum+=i;
printf("sum is %d\n",sum);
}

main(){
int i,sum=0;
for (i=2;i<=20;i+=2) sum+=i;
printf("sum is %d\n",sum);
}

main(){
int i,sum=1;
for (i=2;i<=100;i+=2) sum*=i;
printf("sum is %d\n",sum);
}

main(){
int i,n,sum=1;
printf("n=");scanf("%d",&n);
for (i=1;i<=n;i+=2) sum*=i;
printf("sum is %d\n",sum);
}

int i,s
i=1
s=0
do
s=s+i
i=i+2
loop until i>99

下面几个类似

说明白点，用什么啊？C啊？